Looks Like I Picked The Wrong Week To Quit Sniffing Glue / '64 Valiant Troubles

Question: I eventually want to convert to disk brakes in a couple of years. Can I use 1973 upper control arms on my 1964 9" drum brake setup? The way they look on the internet I'll so no.

No, won't fit in steering knuckle. Wouldn't worry too much about the compression mismatch, you could probably drive it many miles. Besides, slant sixes are a dime a dozen.