Been there, done that, recently!
Fairly straightforward, just takes some patience!
Issues: You'll need to source or fabricate the power steering/hydroboost pump brackets. With my latest conversion the P/O had supplied a vacuum booster for the brakes, so i installed a SBC PS pump with new lines to the box. (no longer a hydroboost system!)
Keep the diesel radiator. Much bigger and cools better than the gas version, but you will have to adapt the hoses. Steel exhaust adapters can be used to splice the two different hoses on the top side. On the bottom use the diesel hose off the rad and a short section of the correct size off the water pump with a adapter inbetween. (has worked for over 15 yrs on my C30)
No need to change fuel sending unit or fuel lines, but, think you have to install a breather vent on one of the three lines coming off the tank. (At least i had too on my 82 C30 conversion)
I removed a LOT of unneeded wiring from under the hood! As for the starter wires, only ran a power feed, and solenoid wire and ran them down in the front of the block (near water pump). Hooked all other power wires to the block on the firewall and connected there. Much easier than running tothe starter.
Keep in mind that you're going to be spinning some healthy rpm's if any highway use! Might be a good idea to put a decent intake, mild cam, towing convertor to maximize power. Eventually i'd like to install a gear vendors unit on mine, but a little pricey and not enough money at present!
Cheers, Eric