I thought the th350 wasn't in production until very late 68, but I'm no expert. the shape resembles the one I just bought from Rick's for a turbo 400, although the mounting tab was on the right and attached to the outboard bellhousing bolt above the starter.Your's looks like it attaches to the very top upper right bellhousing(behind the dist) bolt, like the assemble manual shows for a 68 th400. I haven't been able to find a filler tube for a turbo 400 that bolts to the upper bolt. I believe the one from Rick's which is a GM part is a multiple application part. Somebody with part #'s will chime in shortly with the correct application I'm sure.