80+ 302's had a different balance than pre 1980 engines so you would need to have a 94-95 balancer rebalanced or maybe something aftermarket.
The SN95 Mustangs had the standard balancer so it wouldn't be that big of an improvement. Did you get the lower pulley for a SN-95?
If anything you should have to shim the pulley out because the 28oz dampener you are going to be stuck with should be thinner than the 50oz that the Mustang would require.
For what it is worth, Ford Racing can be kinda flighty on what fits what. They have burned me before on that. Case in point when I was going to rebuild a '78 302 I got a dual sump oil pan kit that fits a 260-302 or something like that (could have been 289-302 like your kit, doesn't matter) and I thought I was golden with the pan dipstick, no dice. Apparently they don't think dipsticks are required on all engines. I also have a dipstick that didn't fit my trans... I have become leery about using their stuff and research hard before I do.
Late 70's Foxbody Mustangs had the dipstick in the block, new pans are available for them. 79 until whenever the 255 crawled out of the woodwork. Don't know of any retrofit kits though.