Here you are Alec.
Measurements to follow tomorrow. Same size for Mk 1 & Mk 3, although mine is about an inch shorter. The base was rotted out & I could not drop the tank down through the chassis, the only way out was through the boot door. That required a reduction of an inch!
I have been told that it is possible to drop the tank down through the chassis as someone has done it but theirs was a Mk 3 based on a Series 3 mine is based on a 2A. Bit academic for me as the bottom & margins needed removal anyway.