hey man'
You are in luck. That is standard Chevy SB center bolt spacing. I was also wrong about it looking like the Stahl.
Sometime today I will place a Canfield SB Chevy Head with ported 1 5/8 ports and a Brodix with 1 7/8 ported ports requiring the the Stahl Spread port desig header , side by side and shoot some pics and post them here so you can see the differences.
Headers for any SB should fit that bolt pattern. Depending on your header needs, a 13/4 should bolt right on. A 1/78 from hooker should fit. Schoenfeld has a 1 3/4 and a 1 7/8 that will fit gen 2 Camaros. and a few other cars.
Ed