3:55 gears to 323 gears

You did say you have 4spd, right? IMHO, stay with the 3.55s. Ma Mopar put 3.55s behind 4 spd SMB. and 3.23s behind automatic for the difference in RPM at highway speeds. Also in your case as mentioned your camshaft. I had a noisey set of 3.55s behind my 340 auto, 10.25 cr 474 cam. I had a nice 3.23 set I swapped in to take care of the noise problem. Actually quite a difference in excelleration performance. And car used to bark second very easily at low rpm, had more neck snap. The trade went to the highway performance end. Higher cruise speed, with more pedal for high speed bursts, cooler, consistent engine temps slightly better gas milage. But if I had a fourth gear like you, I would think it would be the 3.55s for sure.