Thanks guys,
I wasn't expecting such a quick response. That parts reference is really handy, and I've managed to find the pinion for the Blackfoot on ebay. I think I'll get some aftermarket shocks for the Manta Ray, the motor mount from another car with the same chassis might be easiest as I'm not too confident an alloy one will fit, they don't seem to have as many holes as the original. The uprights don't seem to be anywhere though, I'll keep looking and they might turn up at some point.
The one thing I can't seem to find is a new body for the Porsche, are there any others that will fit?