'91 360 for my '73 Swinger?

Yes, if it has the 308 heads I would take it for $300.

There is something about the oil filter mount on those engines, I believe it was 1991's.

I just recall looking in to getting a short block and up to 1990 were fine but the 91's would not take the 90 degree oil filter adapter. Now if your not using the HP 340 exhaust manifolds or certain style of header pipes, then no problems