1200 SP to 1500/1600

Hi Guys

I have a 1200 58 beetle which I'd like to get a bit more power/Tq out of. I was thinking of increasing the CCs, do standard 1500 or 1600 sp cylinders fit the case/heads without machining?

Also what are the really fragile bits on the 1200sp I should replace whilst doing an overhaul. I was also thinking of getting an Okrasa copy cam and maybe a dual solex set up.

Not interested in putting in a later engine coz I think the vintage speed thing is pretty cool.

Any thoughts?

Cheers Dicko.