EMS has patch panels for 1950 Chevies that aren't a bad fit and better than most that will work on '50 88's. I used the inner and outer rocker panels and rear quarters on my '50 88 2dr cedan. Also read atomickustom's post on patch panel success.
call us with the numbers off the firewall tag and i can tell you what will fit, we should have a lot of stuff ems customer servicei 216-541-4585