Small blocks are hard to get the air bled out of when filling with coolant.
There are a few of us that take and drill an 1/8" inch hole in the thermostat to allow the air to bleed up out of the block and heads and intake when filling with coolant.
Small blocks ARE NOT difficult to burp
Drilling the T stat is not a bad idea
HOW TO BURP, easy
Pull the heater hose off, preferably at the heater, the one which hooks to the intake manifold--this is BELOW the T stat and provides an air path. Hold that hose "up" with haywire, etc, I tie it to the hood latch Fill the thing up, and normally you will start to get a dribble out of the heater. If not, slowly lower the hose in a safe area and watch it, until you get coolant dribble. Re connect the hose, squeeze the top hose and re-top. Watch the coolant level, and feel the heads for temp as it warms up, TURN THE HEATER ON AND LOOK FOR HEAT OUTPUT. These two things help insure that it is not over-heating. After running and cooling, recheck, refill.
I have done this for DECADES and never had a problem.