I think the TKX will be "ok" if this is 90/10 street to track time car? And without slicks, that would help too. Also, look at a clutch tamer to help the trans live at the track
https://grannys.tripod.com/clutchtamerdiy.html
NAPA, are you going to take this car to the dragstrip and race this car? Reason I ask is MY '69 Nova SS396 has been 10.40's with a mildish 396/402 and the Polishing Sneakers 427/433. Those were accomplished with a M21 over about 3/4 years, mostly a streetRACED car. Traded for a built PG with 5500 converter. I lasted another 5 years on the street in a '69 Chevelle with a nice 406.
I launched the car @ 5500 with 4.56 in a 12 bolt with GY 9 x 30 slick. I used a Ram 3800 lbs B & B pressure plate with a Ram 3 disc clutch WITHOUT springs.
IF your just racing the car, Ya the TKX won't live, then go with a Liberty LSC5?00 trans.