Bored here in the heat and browsing the web, found that Ergo grips has just released a adapter for 20 gauge 870 that will allow you to use any AR stock and grip on the market, commercial or mil spec. 39 dollars. Just ordered one. https://www.ergogrips.net/shop/ergo-remington-20-gauge-shotgun-stock-adapter/
That looks good, I went the ATI due to not many options but its solid and fits well.
Awesome thanks!