High Compression 390

The 91 is just another 'arrow in your quiver' to make this work out.

This type of engine in a truck with a granny gear will be very strange, at least to me. I always associate a granny gear with the 1960 F350 that I used as my 1st race car hauler with the low compression 292..... 45 mph in 3rd gear up the WV hills on I-64 and in the PA mountain was all it would do. But you shoulda seen the folks scatter and cars scoot out of the way when it was headed downhill LOL....