I'm going to re-open this one, since I just joined the party and read all 9 flaming pages. I think it's interesting that you're asking newbie questions, yet you own 3 other Land Rovers ranging from 1972-2009. I'd have thought some of the basic questions would have been answered when building your SIII.
I have a 1986 110 wagon that I've owned for about 7 years now. I had a Discovery before that. When I bought each vehicle, I was excited about the idea of modifying them. I remember when I bought the 110, I was Photoshopping different colours onto it as I figured I'd be painting it. Wait a minute ...
Guess what. It's still blue.
I also decided I wanted to move my carpc from my old Discovery to my 110. So, I had someone hack a hole in the dash and add in an aluminium box for the touch screen. Later on I found out that I cut up and destroyed the value of > $1000 worth of dash components. Plus of course, the invention of the iPad obviated the whole concept.
I'm with you on building the vehicle you want. Some people want original vehicles, some don't care. I don't care so much. For example, this summer I ripped out most of my rear trim and sprayed Al's HNR on and U-Pol Raptor on top of that. Some may hate it, but it (hopefully) works for me.
I have a 200tdi with a rebuilt turbo, full-width aftermarket intercooler, and slightly modified fuel/air mixture. With my 285/75 Goodyear Duratracs, I can do 0-100kph in about 21 seconds. I run out of gearing at around 112kph for normal driving, although I can go > 120 while passing. A nice cruising speed is about 93kph, and I can pretty much do that all day, on the interstate, on a dirt road, or through a blizzard. I get about 10.5-11 litres per 100 km at that speed, less if I'm going faster. If you can handle those numbers (and the noise) then you're going to be fine with a 200tdi. I carry ear plugs for long solo trips.
Really I think you need to divide your planning into several sections:
1. Safety
I put brakes, steering, and a roll cage in this category.
I'm not the best mechanic out there, but neither I, nor
any mechanic I've ever taken my truck to, has ever been able to get my rear drum brakes working. People on here are probably going to mock and pillory me for this, but that's the fact. Last year I put in new shoes, slave cylinders, adjuster cams, and brake lines, and they still completely suck. I think the problem is that the shoes keep popping off one of the cams. I wish I'd just converted to rear disc brakes.
For the roll cage, I did a lot of research on this one and ended up with a Whitbread Off-road cage. You can see my discussion about this at
http://www.expeditionportal.com/forum/threads/78097-Roll-cage-options-for-my-110?highlight=whitbread . I like this cage over the SD cage, as it's welded together, not bolted. They were very easy to work with, and I was fortunate to be able to get the package shipped for $200 through someone else which kept the cost down. I had it welded up by a fabricator who's also a Land Rover owner, so he understood the details of fitting that are not the same as other applications. He also suggested a new design for how the cage mounts to the chassis at the rear. This ended up adding to the cost, but it's a lot more secure now. The roll cage also provides a large platform for a roof rack, which means there's no need to buy a $1200 rack like you were planning. Just get some expanded aluminium, weld some channel on the outside and put some holes in it. Then you can have it on the top permanently, or remove it too.
Seats can be considered another safety feature. Depending on your height, the stock seats may offer no whiplash/neck protection.
2. Reliability & mechanical soundness.
If you're looking at a new bulkhead, and changing your engine, you may as well do as others have suggested and just go down to the chassis. I guess how good an idea that is depends on the state of your chassis. If you do this then you'll probably end up spending more than $30k if you're paying someone else to do it, but you'll have everything gone over and updated/replaced. I don't know if they salt the roads in CO, but getting a galvanized bulkhead and/or chassis might be a good idea. I'm in the process of installing a galvanized bulkhead on mine. I didn't go down to the chassis as mine's in good shape, but I did sandblast and paint the areas I could easily reach while the bulkhead, wings, and floors were out this summer.
At the same time, you can inspect/replace any worn bushings. You might find that pieces like your panhard rod, rear radius arms, etc., need to be replaced at this point if they're seized and won't come off. This is also a good chance to update those pieces with cranked/adjustable/whatever in anticipation of a lift.
3. Fitness for purpose
This is where you have to be honest with what you're really going to use it for. After some early mistakes, I've come along steadily, based on what I need. What I have done over the last 7 years in this category include (from memory): 12k electric winch (with cut-off switch and another master cut-off switch for the whole circuit), electric cooling fan, 2" OME/Britpart (don't ask, OK ask if you want) lift, 285/75 Goodyear Duratracs, recirculating coolant heater, warmer thermostat, dual batteries with National Luna monitor, seats, roll cage, cranked rear radius arms, adujstable panhard rod, onboard compressor and tank, custom trailer hitch, 7-pin trailer wiring, rear fuse panel, raised air intake, and sealed LED lights.
I had a Detroit locker in the back when I bought the truck, and I really like it. One of these days I'll probably put a TrueTrac in the front. You might want to put traction diffs on your list though as they really add significant capability to the 110.
4. Fun
This is where your paint job comes in. IMHO if you can do all of the above and still have budget for paint, have at it.
