[DarkAlman]

The SA58 is a FAL carbine, the stock foregrip I used is from a full size rifle. It's just too long to fit on it.

Assuming the SA58 is like the KA FAL (assuming you have a foregrip of the right length) the wood foregrip fits with little effort I just needed to file down the metal parts at the back to make it fit snuggly.

The stock is a COMPLETELY different story. First of all it's not hollow. There's a channel on the inside for a cleaning kit that is slightly too small for a stick battery.
Secondly its not wide enough. The real steel stock is shaved down near the back which makes it too thin to drill out for a large battery. I had to make mine slightly thicker and tapered near the back to make the butt plate fit.
Thirdly it doesn't have the right mounting hardware. Although it is feasible to make a real steel stock fit an SA58 the amount of work involved is so great that you might as well make one from scratch... which is what I did.