None of them I’ve seen accept spacers. I have the original Havak in McMillan stock. No spacers. I built a 224 Valkyrie bolt gun for my daughter and used the Bergara HMR Pro stock because it was light and has a spacer system. In her case we were removing spacers.
Honestly at 6’5” I do not think any factory stock will fit you correctly unless it has adjustable LOP system. Be prepared to buy one factory, buy a adjustable stock or modify your new rifle. Almost any stock can be modified.
The Bergara HMR Pro is comparable to the Seekins Havak. I considered the Bergara when buying my Seekins. Both were hard to find at the time so I bought the first one I could find.
Good luck. Hope you get what you are looking for!