At the risk of stating the obvious, do remember that the bodies were handbuilt, so even if you found repair panels from another car they would be pretty useless. The alloy bodywork is a specialist job, preferably by someone who has rebuilt an Ace before, as they can build in the subtle mods and improvements that have been developed over time to reinforce what is after all a lightweight, relatively fragile, structure. Of the three engines, the Ford is the cheapest to restore, but only if you stick to a Ford iron head; the alloy Mays head gives more power, plus the option of Webers, but is hard to find and very expensive. A well fettled iron head with three SUs and a six-branch is probably the best compromise of power and cost. My 2.6 has an alloy head with Webers and I love it, I just keep my fingers crossed that it never warps or cracks!