Okay I find this very interesting.
Primarily, what I find interesting is most of the responses and how confidant you all are that this can not be done. Really anything is possible.
Reason I say this is I am right in the middle of doing the exact thing that Steven is contemplating.
I am converting my 1997 D-90 to a 110 for the exact reasons that Steven mentioned here. I can not bear selling my 90, I have a growing family and need the room, and I gotta have a defender. So the difference with mine i guess is that I already have a 90 that is excellent condition. Therefore I have 60% of a fine vehicle. Now I must say I feel that luck has something to do with it all also. I have been real fortunate to acquire 85% of the parts I need very economically.
I bought a 1983 110 parts care for $5000. It was already apart for the most part. I got a nice frame, rear tub, rear axle, roof sides, roof and extra bulkhead and parts to sell for cash. I had to replace the rear x member and get the frame galvanized but that was not bad at all. I was able to find a used NAS 110 external cage for $1800 plus a trade for my cage off of my 90. I have basically brand new middle doors for $1400. So with the parts sold off my 90, which is a big cash cow, and the great prices you can find out there if you shop hard and long enough I hope to do this project for around $10,000. I have no idea where I am at on the costs so far but I am pretty sure we are on track. I am not saying it can be done for that consistently, but if you play your cards right and are not in a hurry I think it is possible. I will probably end up spending more for sure, but it surely will not be $30K.
To prove my point- right now on ebay there is a 1983 110 for sale that is ending soon and it is at $5600. A possible better deal than the one I found.
So in the end the only way I see to do a 90 to 110 conversion economically is to either find a crazy good deal on a donor 90 or to already own a 90 and find the parts like I have. You can say why not just sell you 90 and spend 10K to get a 110? On top of the fact that you might be able to find a "decent" 110 for $35-$40k, you will still most likely need to put another $10k into it to make it what you want/functional. Also, for me it was a very personal thing. I just am very connected to my 90 and did not want to sell it, plus I really do not want an NAS 110. There are many things I do not care for about them including the bulkhead- no vents, the probable rust issues, the seats, no sunroof, no r380, etc.... I do like everything about my 1997. The dash, the ac, the motor etc.... Plus I can do all the build minus any body work myself which helps tremendously.
Pretty long post but I felt I needed to say it! Lets just wait and see if I end up eating crow and Slade was correct, but I am willing to take the risk to get what I want in the end.
I have the frame back from the galvanizers and will be starting the tear down on the 90 this weekend and hope by mid june to have a 110 rolling chassis with drive train, and bulkhead in place. I will keep you all posted when I can.
Later
Tyler