3.23 to 3.55?

I made this exact switch on my ‘79 Magnum.
Glad I did. I wouldn’t go back. It is just a few hundred rpm more than a 3.23 on the Hwy. at worst.

Performance wise it felt like a good tune up from a neglected engine. On the road, it was a nicer take off and it worked better getting on the Hwy. and going around cars for passing. The sweet spot for the 400B/727 B body with 245/60/15’s was in the 55-65 mph area.

Traveling at faster speeds (70+) required a slight tip in of the TQ secondary side making it thirsty. I’ve only had the car to 110 mph. Non sustained. It was a few mph lower than the 3.23’s but unless you need to be there.... I don’t think I’d worry about it LOL!

The drive feel was nicer. It helped give the car the missing “Pep” I thought it lacked. While it is not a huge gain by any means, it is noticeable and IMO, a delightful enhancement.

The only thing to make this better (and this is totally driver and engine combo dependent) would be an overdrive transmission for a serious rpm drop when in overdrive. Of course the engine build comes into play starting with the cam duration size not being to large as to become inefficient coupled with the torque converter operating in a too low of a rpm range and letting it heat up to much.

Being you run a manual gear box..... never mind.... LOL
But that’s added in for the auto transmission guys.
Figured they might like to know FWIW.

Also, FWIW, I drive off the far eastern end of Long Island to Carlisle Pennsylvania for the meet and I have ZERO issues with Hwy. traveling. It takes me near double your time to get there unless I hit traffic through N.Y.C. just right. Not a fan of 2 hours in traffic to travel a few miles.