...My 1964 Valient Slant Six Build...

Best laid plans....can't have it both ways...one side will have to give.
You CAN, however, drive a pretty beefed up slant on a daily basis. My guess is that the performance will stop just before you get into the "is temperamental and requires lots of fiddling" point for it to be a true daily driver.
I suppose that didn't help a whole lot...