2 or 3 GM pellets crushed up were good enough for head bolts going into any block and was the fix for Toyota years ago which saved them millions in a recall. Bars leak with the pellets were good for me in the past. Years ago if the tube was on the outside it was cut near each end and carefully double folded over using needle nose pliers. A 7 psi cap was used. If you don’t use a recovery system make sure you leave the coolant 1” down.