After installing a set of Hooker S/C longtube headers, we discovered that the 'longer' old style starter wouldn't fit. It would contact the header before the bolt holes lined up. I understand that GM made a smaller starter for the 305, same basic design but not as long. This starter probably would have worked, but would've still been close to the header.
The solution we used was to install an LT1 Corvette starter in the car. This is a mini high-torque starter. It bolts up with no problems IF you have the smaller flywheel(152 teeth, i think). To tell if you have the smaller, without counting each tooth, measure across the flywheel. The smaller one is 13", the larger(168 teeth, I think) is 14".
The LT1 starter wires up the same, and is well clear of the headers.
The only drawback was the price, about $139(reman.) from a parts store.

Any other questions, let me know

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"Gonad are useful for their intended purpose,
But they're no substitute for Brains!"

Redbird
Bayou Motorsports
87 Firebird
Delta Region SCCA
#68 ESP

 

You got off cheaper than I did. I had the same problem & used a Tilton mini-starter because that's what the parts store had & I wanted the car running. $200 cha-ching.