Hi, congrats on the purchase.
The most common modification is the front crossmember as the holden engine and radiator don't both fit. FYI I posted a pic of mine (custom made by someone back in the 70's) in another thread:
http://www.aulro.com/afvb/series-i-l...ilemmas-2.html
It looks like yours is the original crossmember so ive no idea how its all fitted in- what does the radiator look like?
I am in the process of having my 186 taken out, but that's mainly because the gearbox is kaput and since that needed to go I thought I would get everything done at once (going to a LR 2.25, so still not original but thats ok). I wasn't going to sell the 186 as its been with my car for 40 years, but since its perfectly fine its probably better being used rather than in my garage, so if you decide to stick with a holden to get your LR running, PM me to discuss if you want.
otherwise have fun and good luck :)

