My take on buying parts ahead of time is don't. Well for me anyway, I can't plan that far ahead. My car has taken 5 years of building and various delays. It went from a flathead to a caddy to a 429 and now has a 260 I think will be the last incarnation.lol I have owned enough different frames, sets of headlights, wheels, grill shells, valve covers, rear ends springs, well I could have built several cars. I guess what I'm saying is that your tastes may change and all those parts you thought you might use could end up on a garage sale a few years down the road. There will always be parts.