Another thing to worry about when it comes to getting the distributor in far enough is that it is possible (at least in GMC engines that use the same distributor) to get the distributor gear to mesh with the cam gear, but the tang at the bottom of the distributor shaft isn't in far enough to engage the oil pump properly. Happened to a friend's just overhauled 270 GMC. Had about 5 hours of use when oil pressure went to zero. He thought he got it shut off immediately, but an autopsy showed the need for another overbore, new pistons, new bearings, cutting the crankshaft again, etc. Detailed analysis showed "witness marks" on the very end of the distributor shaft and the oil pump shaft.
In the GMC engine, the gears start to mesh about 4/10" before the tang engages the oil pump. Probably similar in the Chevy engine. Below is a drawing I did of the engagement that I measured on the 270.
I know you don't have this problem. I'm just saying it is something to watch out for while inserting the distributor.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
