Beginner Road Track Racing: Feedback on Engine Options Wanted

TT5.9mag said
From someone who road races (less frequently now than 2 years ago) in a well prepped stock class Miata, and a Porsche 911, my advice would be to buy a cheap car (Miata’s are perfect) throw a set of brakes and tires/wheels on it and go have fun. Just to get used to it and see if it’s something you’d like to pursue with an older vehicle. It will take a LOT of work to make a 69 valiant competitive. If you don’t enjoy it the Miata has good resale and you can get out fairly cheap. This plan also gives you time to develop your driving skill and you can race while you build the 69, if you decide to. My opinion only. Have fun!

I appreciate that advice and get where you're coming from. While I hear you, I'm confident I'll enjoy road racing based off my motorcycle days and riding passenger at the track in my buddy's Audi. For now, I think I'll be extremely happy with competing against the clock as I learn. One of my goals of the engine options I put together in this thread is to keep my expectations and budget realistic so that I'm not too deep into funding the car if I decide it's not for me or if it is for me and I outgrow the car's capabilities. I can reuse just about all the upgrade parts on a street project and sell the car with its stock suspension for probably more than what I paid.

Have you ever raced your classic Mopar?