On January 13, 2021, Mitchell Kahn wrote:
"The Borg and Beck 3 piece I bought from British Parts Northwest (10 spline) certainly bolts up but there was a small amount of interference as you can see in the bellhousing. I did drive the car, and the ticking as the bellhousing was shaving itself subsided to almost nothing".
After a few email messages and several pictures, we finally figured out the MGA clutch interference problem. The brand new Borg & Beck pressure plate assembly (clutch cover) has protrusions on the sides that touch the bellhousing. The interference will be notably worse once you depress the pedal to disengage the clutch, pulling the pressure plate more rearward. You will be very lucky if this does not break the cast aluminum bellhousing before you can cease and desist.

This is high starter gearbox, very late MGA 1500 and all 1600 cars). There must have been a recent change of supplier for these parts, because we never had this problem before. Pity that a very reputable and well know supplier has changed from a good part to a faulty part. Now we need to notify the retailers, and hope they can do something with the manufacturer to get this problem fixed. Meanwhile, grab a hand grinder and grind a bit more relief in the bellhousing at this point to give it little clearance, and it should be good to go. Just hope you notice this problem before you get the engine back in the car.