I wish him luck but there wasn't a whole lot made for these cars back in the day, and not much has survived. Charlie Price
http://www.vintagespeed.com/ sometimes locates str8 stuff but it's not cheap. He had a finned aluminum high-compression head at one time, about the size of a surfboard. Most evertyhing that applies to any inline will work on a str8, compression, more carbs, cam & exhaust, but has to mostly come from owner-fabrication and machine work these days.