[400TT]

Well if you are happy with LS1, it will be easiest engine to approve. And there is plenty of LS1 info/assistance on this forum.

The engine bay in those old DRB's is not exactly big. So expect clearance problems with LS1, especially around exhaust manifolds to firewall next to footwells. Also height(bonnet clearance) is going to be an issue, DRB lifted the body up in 2000 to help with clearance. Classic Revival is also a very tall body, so that's why they have no problems with clearance.

LS1 will go in, but it will be tight. Lots of other people have shoe-horned bigger engines in an engine bay like yours.

Built Harrison with my brother and used Lexus 1UZFE 4lt engine. Beautiful engine. Hasd140k+ on it when we bought it 3 years ago. Has been flogging around race trace on average every couple of weeks and plenty of road km's. Now has T70 turbo fitted and still going strong. You don't see that sort of engine life/strength everyday.

Peter Ransom should know where dealers are and more importantly where the best(easiest) engineers are.