May or may not be running into a little dilemma on a job. Curious what others have for a crank to crank measurement and what exhaust you're running.
This setup is 34", afr heads on 9.8 deck bbc, cmi sport tube straight back. First motor in looks like the headers are going to hit.... Cmi lists the headers as 33 3/4" with stock heads outside to outside.
I have a mock up of the second engine to go in tomorrow morn but curiosity is killing me!

I'm slightly under 34 if I recall. Stallings green headers with a little room to spare

Mine are 33 1/2" centers. I had some CMI E-top headers ordered that were mitered a little to give me the clearance I needed. I have about a 1/4" clearance between the t-bolt clamp and the header on the other engine.

With the 9.8 deck, you should be good. It will be VERY tight though. I've done the sport tubes on a 9.8 deck with Brodix heads on 34" centers and you couldn't fit a piece of paper between them. They would actually touch ever so slightly when it ran, especially in rough water. Didn't cause a problem though. The tailpipe clamps are whats going to be the issue. The headers should clear but the clamps will hit.
Eddie

We lucked out, 1/4" between the tubes. The flanges look plenty far apart, but we shall see. Clamps coming next week. They sure dont give those away!