i have a 65 lark.300 4 barrel. change intake gaskets front and rear seals leaking (typical) come to find out that between the pass rear intake and exhaust runner i have a lovely nice little hole. so i had a friend who is a guru welder get in and shore it up pretty good. however there are some some small crevices i need to try and j.b. weld shut. so i am looking for a back up. a known good mani. or if anyone knows if they still make gaskets that block the rear crossovers. i should have just left the carbon in there! it does not see cold weather anyway. dooooh!
May want to try drilling and tapping a hole and install a cast iron plug. 1/8" NPT is the smallest size out there. Grind off the heat of the plug and it should be invisible.