Gutted for you about the frame - bet you were well p'd off when you found out. May be worth asking on 16vminiclub too - someone may recognise it.
From what I've researched and learned, the frame doesn't look like it's based on a Mini frame as the towers are different. According to the sticky thread in the Vaux section on 16vminiclub, there are only four commercially available frames available : -
TerryG (a member on 16v) which is Mini subframe based, so that rules that one out.
AMT which doesn't use Mini suspension like this frame does - they use a type of rose-jointed double wishbone system whereas yours looks like it uses a standard Mini top arm.
Ask restorations who are/were or may be producing frames using the AMT jigs.
Allspeed and as you say that's definitely not one of theirs.
So that leaves a home-brew, but if it is it certainly looks like a lot of thought, work and fabrication has gone into it. The main thing I'd be concerned about is if it is in fact for the correct block, followed by the strength/quality of the welding on the frame, although as I said it does look like a pretty professional job.
JR
Edited by jayare, 02 April 2009 - 10:03 PM.