Oddfire Distributor Didn't Work On Dauntless

So while my heads were getting reworked I took a look at the hei distributor I was running and it was an even fire! So I pulled the trigger and bought an oddfire hei from rock auto for a 75 Buick Skyhawk. The oddfire distributor looked just like everyone said with two blank lobes on the cap. After I installed the heads, made sure I was TDC and found info on how the even and odd should be setup on the plug wires/firing order, I attempted to crank up ol Rosco. Well, he backfired through the carb so I began fishing for the sweet spot with the distributor and got backfire through the exhaust...and back and forth. As a well lets see what happens, I re installed the even fire hei and he fired right up and purred like a kitten. I've verified the engine casting number as an oddfire, but how is it an even fire hei works and not an oddfire one?

 

Ok, update...the hei did work. After having to take the heads back to the machine shop that had just reworked them so they could do it again.