I've driven or owned every 60 series ever made to include all the diesel variants. I've even helped with a 2FE conversion as well. I prefer inline six engines over V8 conversions.
I hunt, fish, haul building materials, haul canoes, and haul dog teams around the north country. I will say that the mess of well aged vacuum actuated stuff on the 60's needs to be removed for your own sanity. The 62 series benefits greatly from the nomad valve body. It's almost a must-have if you tow.
My next project vehicle is going to be a rust-free fj60 with a built 300 cubic inch, inline six ford engine. I want a reman fully synchronized zf five speed manual and a reman np205 transfer case. These are really good engines, and will be PERFECT for a land cruiser-style power delivery. How about 350 ft lbs of torque coming in at 1800 rpms? All the UPS brown delivery trucks had these engines at one time. Heck, they even came in 3/4 ton ford trucks back in the 1970's.
They offer the same reliability attributes as a toyota F motor: Gear driven timing, pushrods, 7 main bearings 2 gallon oil capacity,.
BUT you can use the following:
Aftermarket forged 390 ford pistons, forged connecting rods, roller rockers, high flow intake manifolds that accept all sorts of small four barrel carburetors. Way more affordable to build, than the venerable Toyota F motors. Many of these 300 cubic inch ford motors are running around here with over 300,000 miles on the original engines. These blocks and heads were cast at the Cleveland plant. No joke......I have a FORGED STEEL crank shaft that came from an industrial 300 inline six ford engine. That's at machine shop, and the boys there are drooling over this rare gem. It needed way less work to balance, than the last 2f crankshaft I had done up.
The 12ht has great low torque, when that 260 ft lbs of torque comes in at 1800 rpms. For me, it's about getting a vehicle to start at 50 below zero, I've no love for the diesels, though the 12ht is a lovely land cruiser engine.
When I do get to puttin all this torquey, forged steel goodness into a 60 series, I hope it doesn't twist the land cruiser into a rotini pasta noodle!