What year is the 318? If a simple rebuild is in the works, specify a 67-70 piston. This is the tallest of the 318 pistons meaning higher compression with no machine work. My Demon has a 68 318 and 302 heads. We've measured the CR @ 9.3:1 with nothing more than a little clean-up on the block surface and heads.
The parts situation in Central Texas isn't what it used to be since Dr. Mopar closed shop. But I've gotten stuff from Harold's in Briggs, Texas Acres in Harker Heights, and Pick n' Pull in San Antonio all of which are around an hours' drive from Austin. Way back in time there was a Mopar club in Austin (MMCA,
http://www.mopar.org) that may be a good source of leads for parts.