1967 and power brakes HELP!!!

[poldenbuttel]

I have looked everyware for this info, I hope someone can help me. I have a 67 with 72 spindles disc front and drum rear. I want to add a power brake booster, I have seen s-10 boosters on these trucks but I can't find the right firewall to booster bracket. Evberything I find will only fit two of my four studs. Should the booster not bolt to the firewall with all four studs? What year model bracket should I be looking for? I think the stud pattern was like 3.5 x 2.75 inches. Also I need a ashtray for this 67. The aftermarket stuff will not fit as my ashtray is made into the dash and is not a bolt in. So looking for a factory 67 ashtray or a link to a supplier. Thanks