So i turned my rear tire and marked the driveshaft and it turns about 3 1/4 times in one tire spin so i assume i have a 3.21 or 3.23 gear ratio or something of the such. what im wondering is if that is good for cruising and MPG. if not, what would be a better ratio for that but still with a little kick. 3.71?

 

That's a pretty good ratio for highway cruising, and mileage. The 3.73 would give a better launch, but you'll lose some gas mileage. I'm running 3.41 in my '71 behind the 427, but with the extra torque I don't need really low gears, and the slightly better mileage it gets is better. The BBC needs to cruise at lower rpm's also.
If you went with 3.73's you'll find your cruising rpm's will probably be around 3,000 rpm at 60 with a low profile tire. My gasser is using tall 28" tires and I am around 2800 aat 60mph, but low profiles will bring the rpm up higher.
I'm thinking of going to an overdrive 200r or 700r4 this winter to make freeway rpm's drop about 30%.

 

Yeah,i am running 3.73 in mine,with a 28" tall tire,i am also running a 4 speed though so it may be a bit different than an auto,but i am running almost 3,500 rpm at 65,and roughly 3,000-3,100 at 60.It's been a while since i drove the car so i'm going off memory,but i know those numbers are real close.Only complaint i have is the motor sounds like it's screaming at those rpm's.

 

You think yours screams. Try having 4.10's with 26" tires!
Oh, and both a 4 speed manual and 3 speed automatic have the same 1:1 final drive.

 

Haha,yeah i could imagine how it would be with 4.10's and just about any tire size haha.

 

It's fun though. And mine is just a local street toy anyway. I wouldn't go lower than 3.55's on a car that did highway driving, unless it had an overdrive trans.

 

I'm thinking of going to 4.11's when I go to the overdrive tranny. My neighbor has a complete 9" Ford third member, and I may be swapping in a narrowed 9" Ford in my gasser at the same time this winter. He's also got a new set of Richmond 3.70 gears for a 9" so that might be another option.
My 10 bolt Pontiac rearend is holding up well, but the lure of a 9" Ford is still calling me!

 

With mine im going at about 2600rpm's at 60 with 26" tall tires. but another thing im wondering is with my TH350 trans, when im going through the gears, what should it be shifting at because if im just cruising and it shifts from 2nd to 3rd, it shifts at like 24/2500 and then the rpm's drop to about 1500 and that seems a little low in my opinion. about what should it shift at if im not accelerating too hard?

 

Just wondering what does your car turn at about 60 or 70 mph with the 26" tall tires. I'm thinking of going to that same 4.10 gear and I also have 26" tires. Right now I have 3.08 and 4 speed stick and turn 2900 @ 70 mph.

 

At 60 mph, you're looking at 3,250 rpm. At 70, 3,750 rpm.