Newbie with a V50

Hello folks.
Thought i'd poke my nose in and say hi.
Bought myself a '76 V50 (pre restriction) last year and have recently started to get it on the road. It was laid up in a garage since '88. Frame has some rust, but nothing worrying, which is nice.
Anywho, got the thing started and all electrics working etc, so is ready for an MOT, which is good.

I have bought a V80 engine on ebay to fit to the bike as i wanted a bit more oomph.
Received the engine today to find a massive crack on the main casing, so is knackered, must've been done in transit though as it's leaked fluid everywhere.
My question is this, does anybody know whether i can fit all the bits and bobs from the 80 into my 50 casing? I notice that the 80 appears to run electronic ignition as i can't see any points (or the nice points inspection plate). As stroke appears to be different, i assume i can't just dump barrels/piston/carb and exhaust onto the 50 botton end?
I'm torn between returning it, or if there is scope to match bits up, keep it. It was cheap, but still more than i'd like to throw away!

Any help would be greatly appreciated. If mods wish for me to post move some of this to the technical catagory, i am more than happy to so. I aim to be active on here rather than a 1 post wonder!

Sorry cant help with V50/V80 interchange of parts, but you should reject the damaged engine & get a refund on you money.

Hi John,
Unfortunately i bought it outside of ebay, so no real stand point through the normal complaint system.
The engine was very cheap, which is why i am considering the swapping of parts as an option. I have contacted the seller, but he of course hasn't responded yet.