Mercury borg and beck pressure plate

[skidmarks]

My understanding the 49 to early 51 mercury borg and beck pressure plate is 10". I was digging out some stuff to swap a motor in my 40 ford. 53 merc motor 49/50 tin merc bellhousing and a 49/50 merc flywheel. Got the new pressure plate out and it bolts up but the contact surface measures 10-1/2". No clue were it came from and no box. Only number i could find is 1773.

Couldnt find any info on it. I guess the only real question is will it work?