Actually it's been simple, just time-consuming due to stuff happening elsewhere.
Drivers side engine mount needs making fit or re-fabbing completely, bringing it very close to the oil filter.
300 rad/IC is larger so the bottom brackets need cutting down and re-making to suit.
My 90 needed a new engine bay loom making up, so much of it was original 1989, stiff and crusty .. I suspect it may well be worth doing the same for the rest of it eventually!
Heater pipes need cutting down a bit, radiator top hose is different, as are oil cooler pipes and intercooler pipes. I bought 6' of pipe from Pirtek and will use the Disco oil cooler fittings so they fit correctly.
Exhaust needs some cutting and re-welding to suit.
Lots of fiddly bits, on mine air filter brackets, throttle cable, heater cables all needed tweaking ..
Still not finished or running yet, but close to .. Not been working on it all this week ...
