just looking at buying one and wanted to know what kind of aftermarket is out there for power and such things

There isn't really.  Engine swap, the 970cc from an Sj-410 is supposed to be a pretty easy swap.

can u use anything from a sammy

Nothing much but those old two stroke engines do tune quite well. Not much point getting radical if you want to retain  bottom end power but some attention to squish clearances can make a reasonable difference.

You may want to sit in one first... They are really, really small. Anyone over 5' 8" is going to be cramped up. Specially if you have a prosperous waist line.

-Eric

Have a hunt around for a F6A or K6A 660cc turbo engine. They bolt in on the same engine mounts as a SJ410 engine. If you want the wacky option, one of our club members chopped a 13B rotary engine in half and put the single rotor in his LJ50. Because it  was a single rotor it overcame the crank flex issues that they can have and would really rev.