replacing clutch on 70 sb with 4 spd manual trans. Looking at flywheel ring gear, seems some teeth are worn down a bit (about 25%) whereas most teeth are very good with no wear. My parts salesman told me to replace ring gear myself, by heating old one cherry red with acetylene torch and hammering off with punch and hammer. To install he says heat new one cherry red and drop it on flywheel. Is this correct install technique. Is it a simple install. YOur experience would be appreciated.