Is this new motor in a car now? Can you drive it? Or, can you compare dyno graphs from both motors?
I think Racer X is getting a little "cranky" lately...sure seems to be bothering him that anyone would even consider putting a big block in a Cobra.
In a Kirkham or an ERA, the FE would be a no-brainer. In a SPF, it's a toss-up.
I like the motor I have in my car, which is somewhere in between your present motor and the one you're considering: plenty of oomph, yet with enough room to work around. I've never really wished for more horsepower and what I REALLY wouldn't want is increased gas consumption. On the other hand, if 100 miles is a long drive for you and you like the way the big block looks (and sounds-a big FE just sounds cooler than anything else) and you don't mind having a motor which
may require more maintenance, hey, it's YOUR car.
I've seen and heard of more guys going from small block to big block than the other away around, if that's any help.
And yeah, the 3.73 gears are pretty much useless, even with a smaller motor. Figure in the cost of new gears and set-up for the differential on this project...also likely new half shafts if you have the Ford 8.8 and, if you're upgrading the half shafts, you might as well go to 31 splines, which would mean upgrading the differential as well. Ditto the U-joints. You DO have a good driveshaft loop (or loops) don't you? The original SPF is NOT. Your tranny may take it, may not... You'll also need new headers for the FE.
And then how will your car drive? I doubt you'll gain any "driveability". Depending on how the engines are built, the FE may not want to run as smoothly at low RPM's as the 351. It'll be hotter and noisier and may need race gas, depending on the CR.
Bottom line? If you're contemplating this change to increase driveability, I think you'll be disappointed. If the WOW factor and a HUGE horspower increase are worth what may be a major expense and possibly an increase in aggravation, well, that's something YOU'LL have to decide.
Lowell