The 3.5 liter V-8 is much the same as the old Buick 215 cu-in aluminum V-8. There are still lots of aftermarket parts available for them. I've toyed with the idea of putting a V-8 in my Alfa Spider and a Rover motor would be near the top of a short list of motors I'd pick. Edelbrock has intake manifolds for the to convert to a carburetor:
http://www.edelbrock.com/automotive/man_rover.html
Ebay usually has lots of 215 parts.