Why not just go with the 2.9i out of the Sierra though? It'll be plenty powerful enough to propel a lightweight car although I really do think you're going to have major problems doing the 4X4 thing.

D.

my father in law as sat in his garden a xr4x4 with a boa conversion in it from my old fsoc club days im trying to get him to it let go you know the old saying ill get that back on the road soon and he wont and a few 2.9 12v,s if you need anything im hopefully cleaning the garden out (to make room for a full blown garage workshop i might let him use :p ) this weekend or next