I currently have a 8.75 rear w/ 742 pumpkin and 3.23 SG.
I am in the process of trying to put together a nice streetable 451 combination in a 69 B body.
This car will be a used only around town and as a highway cruiser, no track. But I also would like it to rip on the street when needed.
I really would like this car to perform well down low as it will not see much time in the really high rpm range.
Will I be sacrificing alot of power if I stick with my current gearing? I was thinking 3.91 or 4.10, but then will I lose the streetabilty?
Btw, I dont have a cam or TC selected yet as I am trying to match up all 3 for the best performance.
Thanks for the help.

you could go up to a 3.55 but I wouldn't go further than that, unless you get an OD transmission

my 438 (same combo as your 451, but in a 383 block) had 3.21s with a 28" tire. in 4th gear (1:1) it would do around 65 with something like 2300, 2400 rpm.

but I have a 5th gear .64 OD...which I couldn't even think about using until I was going at least 75.

so I changed it to a 4.56 rear gear and can now do 65 at 2200 rpm in 5th, or 75 at 2600 rpm

oh, and with the 3.21s the 438 would roast the tires in 1st gear from a 20 mph roll, so it'll still be fun on the street!