Slant six performance parts

Hello, this is my first post here. I recently purchased a 68 Dart 270 with a slant six 225. I use to have a 69 model years ago with a slant six but never did any performance upgrades before I sold it. But I definitely want to get some performance out of this slant six or do an engine swap. Think I found a 8 3/4 but need alot more stuff. Love the style of the car but I need some performance before paint and rims.

I've been reading posts here and researching online for performance parts. I tried to contact Aussiespeed but they're hard to reach and there's no number to call in the US. I received one email response from Aussie and nothing since I sent two replies. I talked to Clifford no problem but I read alot of stuff that makes me wonder if I want to send money their way. Maybe a swap is the best route.

Any suggestions on who to contact for parts would be appreciated.

Thanks,
Maritimer