Lost Frost plugs

What Engine? 360? should be 1 5/8 or 1.625. I'd get brass ones. Can be done in the car but not fun. Clean up the bores with 80 grit sandpaper. Coat bores with RTV or Gasket sealer. Impact socket to fit in the cup and BFH.

We tried to get in to measure with a caliper and the best we could do is 1.48 ish..

Since you cannot hit directly, how do you make sure it goes in straight ?