1970 225 slant six parts wanted

Before you go shopping for parts, keep in mind: picking parts because they look interesting is usually a good way to waste money and time, because it's backwards. Much better to figure out your goals for the car — what you want it to do that it doesn't do now, and what you want it not to do that it presently does. Be as specific as possible in terms of performance, economy, driveability, and cost. Then once you've worked up those goals, share them and you'll get solid advice on how best to proceed.

There are lots of options for hop-up parts. You'll hear the name "Clifford" come up, but be very careful before you decide to spend any money with Clifford. They have a long and ugly reputation for being a bunch of clowns; see for example here, here, here, here, and here. Much of what they sell is inaccurately described, and a lot of it is not even slightly cost-effective.

The good news is that you don't need to go to Clifford to get hot rod parts for slant-6s; there are lots of other, better options. See for example Dutra Duals and header options discussed in this thread and this one, Erson custom cams, HEI ignition upgrade, Mike Jeffreys windage trays, Super Six (2bbl) conversion and a different way here with photo documentation here. Hurricane intakes, other exotic intakes. Hi-perf engine buildup here, high-perf parts and build info here.