I have a TBI 1 pc seal 2 bolt main 350. it has three bosses which i drilled and tapped. i have the spider, dog bones, roller lifters, cam retainer, and all bolts to go with it. parts came from a vortec motor. my issue here is should i drill and tapp for the cam retainer or use a cam button? motor came from a 1994 4x4 c1500 truck and is going into my 1982 c10 and will be converted to carb.