M52 engines have one hole in the intake elbow.
M50 engines have two holes in the intake elbow.

An M50 will fit your MAF fine.

So adding 5mm to the bearing side of the fork and using the standard M20 release bearing works just aswell as the E21 bearing? Is there an exact number in mm to add on or will 5mm be ok? When i did my conversion on my M50 I modified the bearing so it sat further forward but doesn't seem to have done...

Looks like you got a bit of a steal at £400, looks smart.