The Salisbury 7HA axle has a tube diameter of 2.25”.
Original factory U bolts to my 1972 +8 with 6 leaf springs have a measured internal dimension of 5.25” they are from ⅜ stock with a BSF thread.
Later MMC dealer supplier U bolts in my possession are 5.375” in length but came with SAE UNF threads.
MGB ‘banjo’ axles 1963-1967 also have a tube diameter of 2.25”. Replacement U bolts supplied by the “MGB Hive Ltd” have an internal dimension of 6”, they fit with MMC bottom plates, are from ⅜ stock with SAE UNF threads.
BMC part no AHH6452 and are £16.25 for 4 including delivery.
A number of MG suppliers offer lowering kits for the banjo axle and/or long U bolts. The lowering kits are advertised at +1”. Again courtesy of eBay the price is about £35 delivered.
If you want heavier duty U bolts, Mulfab sell a set, these are from 7/16” stock and will need matching bottom plates. The internal dimension of these is 7.5”. I believe Mulfab supply matching heavy duty Rutherford bottom plates as well as HD U bolts with ears for lever shocks.
If you go with MGB parts, be aware that it is only the Banjo axle that will interchange, the ‘tube’ axle fitted MGG GTs and later roadsters has a larger axle diameter of 2.5”. The axles (English & Atlas) fitted to Fords are also 2.5” so will not fit. Going the other way A series engined BMC cars (M1000, AH Sprites, Midgets) are I believe 1.875” in diameter.
