Other than the internal upgrades like sprag,billit drums and LBA as well as better shafts the weak areas were the pump drives and the front cover housing that the bellhousing bolted to.These were pron to crack and even split at the bolt holes.On one attempt to fix the drive issue I installed a belt driven pump to eliminate the spider front pump drive,Another issue with the clutch driven pump drive required a 3 finger Ford style clutch.The other problem was the critical runout to the centerline of the crank anything more than .020 could cause the front sleeve to break.I finally gave up and gave away 2 B&Ms and 1 Fairbanks and went to converters.