For something where the basic longblock is left alone i think the 5.2Magnum would do quite good. It has more compression,better heads and rollercam from the factory(yeah i know the later LA360s came with rollers but most didnt)
This comes from the perspective that i daily drive a 5.2Magnum in a ram1500 and its not a very rare moment when the thought passes thru my head how nice that 5.2 would do in a lightweight A-body,it just pushes that ram around so easy at low rpm and even with the converter locked up and with a nice litle push thru the middrange in a heavy car with barnstyle aerodynamics.
Just a carbed intake and a set of headers on a 5.2 in an abody would probably do wonders in extending the powerrange alitle and would probably be enough to equal a stock 340abody.
