Ak47 and Ak74 is roughly the same length, the short Ak would be the AKSU. Which is even more different regarding muzzle break and hinged top cover to name a few.
Of course the 74 is 5.45x39 vs. the 47 in 7.62x39
Ak47's use wooden handguards and the more modern 74 would often be using plastic for handguard and stock, there are folding stocks made from sheet metal and solid plastic. I've never seen a folding 74 buttstock made of wood. The 47's stock is an underfolder and of metal of course.
The muzzle brake is quite obvious on the 74 and on the 47 there isn't any. Magazines for the 74 are mostly in plastic and are less curved then the 47.
The 74's buttstock has a groove cut in it, the 47 hasn't, sling mounts differently on the butt.
To me they are a lot different, but unless it is very important, just go with the 47?
Then again, i've seen quite a lot of mix and match on ak's all over the place, some mix wood with plastic where it normally shouldn't be. Hungarian pistolgripped handguards on Russian ak's, Chinese pistolgrips on Yugo ak's, AKM muzzle brakes on 47's etc. etc. obviously there have been added spareparts from where spareparts could be found.
There are also quite a lot of bastard ak's from the American market, short 47's, 47/74's with no buttstocks, "pistols" and what not
The butt should be easy to take off but you might end up with 2 prongs that sticks out of the receiver.
Here's a good site on ak's:
http://tantal.kalashnikov.guns.ru/And:
http://world.guns.ru/assault/as02-e.htmMm? Well, somewhat confused but right out of my head...