I have two SA Rem 700s with HS kits and 10 rd mags. They dropped in no problem at all. One into a HS Precision HRT stock, the other into the factory 700 varmint synthetic stock.
I have a Long Action Rem 700 with Badger Ordnance bottom steel that uses AI mags. The 300 Win Mag 5 rd mags fit 6 rds of 6.5x284 and feed nicely. I'm sure Badger makes these kits for SA as well - -and they use AI mags...
I remember making "minor" tweaks to the inletting of the stocks to fit all three. No one more than any other. It is crucial to test test and test, and adjust as needed to make sure the mags feed properly. Thin washers (included with HS kits?) on the bottom side of the action screws are used to adjust the angle for proper feeding. Something to pay attention to when taking it apart. One of the SAs uses one washer. The others are all good without any.
If the rifle is properly bedded, adding the kit, even with these washers if needed, won't affect anything if oyu toque everything properly.
I like all of the kits.
I "heard" that the mag from "Stocky's Stocks" can fit a slightly longer .308 COAL than the HS kit.... but I haven't seen it myself, and my throats are all short on purpose so my loads fit in mags.
The 300 Win mag magazine with 6.5x284 in it has room to spare....