You a new guy? Welcome to the 'bolt, doode.
If I understand you right, the passage you're referring to is drilled from back to front of block, thru the lifter bores, right? The lifter galley is fed from both front and rear cam journal on a '58 235. Now as I remember, the freeze plug/galley plug set I got with my '60 engine included 3/8 soft plugs and 1/4" socket head set screws for plugging various passages. I know the 3/8 outer hole was plugged on my engines with the soft plugs, but couldn't see if the 1/4" threaded plugs were installed behind that. You'll need to ask a machinist if another guy here can't come up with the right answer.
Whoops, after reading your post again, the lower LEFT side of the back of the block would be the driver's side, correct? Thats the main driver's galley that feeds oil from the oil pump outlet to the main bearings. Same thing tho, 3/8" soft plugs installed, no idea whats under that. Perhaps the correct length of threaded 1/4 socket head set screw (as provided in kit) would be the right thing to use, as this galley is under full oil system pressure of 20 to 50 PSI.
BTW, you got cam bearings in the block yet? I think those have to be installed first before any plugs or anything. Make sure to run a rifle brush thru all oil passages to make sure they're clean.
good luck
chiphead
