Skyhawk 90 Basics

I am looking to upgrade my 7 year old from a Predator 50, and have some basic questions. I have a line on a relatively inexpensive Skyhawk 90 that needs a new top end.
First, it appears that the Skyhawk 50 and 90 had the same frame - is this accurate?

Does anyone know if the 39.2 mm crankshaft (50cc) can be swapped into the 90 cases along with a 47 mm cylinder to build a 70 cc engine?

Assuming I put on +3 +1 A arms, replaced the front and rear shocks, added some wheel spacers to the back, and got the engine back in order, how do these quads do for trail use. Is it still worth taking the time to build one of these, or is it easier just to buy into a DRR or Apex?

Thanks for all responses.

Kasea is a good machine you dont want to use a 39.2 in a 90 case. 47 willbe fine . Drr is alot wider than the kasea and unless you use DC double arms your no futher ahead . Then your adding cost. A arms and shocks youll be at least 2000 in suspension parts plus your topend and cost of quad . Again kasea has a lot of posiblity.
DRR drx2 70 is 44 wide, plus 2 rear swinger ,19 in front tires and disk brake all the way around. Metrakit 90 kit when your ready to add more power to the 70 . Disks would be another 800 for the kasea conversion. DRR drx2 70 lc to your door around about 2600 . But your buying you be the judge.