While of no help to you now, anecdotal stories of fitment issues like this with aftermarket parts have made me wary of using them.
Instead, I am in the process of fitting early OEM factory non-cat manifolds, which you know will fit perfectly, and are significantly more compact as you can see.
Granted, these may not flow as well as a set of proper equal-length tube headers. But I doubt that any substantial performance differences could be noted during most circumstances.
