I recently won an auction for what appears to be a vintage V4 big muff

http://www.ebay.com/itm/Vintage-Big-Muff-Fuzz-pedal-/221162002901?pt=Guitar_Accessories&hash=item337e4859d5&nma=true&si=ctMFbFpgagdhm0CwujwwTeyaJZY=&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

I got a great deal because its missing the back piece.. Does anybody know if all big muffs have the same dimension? Could I go into GC and buy a new big muff and use the back from that for my vintage big muff? Anyone have any experience with this?

It seems a little silly to spend $80 something on a back piece but I don’t know or couldn’t find anywhere that sells this part.. Only knobs, pots, switches, etc but not for this back piece. Anyone have any other suggestions? I’m really excited about this pedal and I can’t wait to receive delivery! Also I’m not an expert on vintage muffs but from the website and looking at the pictures it appears to me to be a V4. Can anyone verify this?

Thanks a bunch!