Gear Recommendation

[Nosub4cid1966]

Ok, I have a 66 coupe with a 5.0 based motor. Nothing exotic just a 5.0 HO with HCI swap retrofitted to carburetion (front sump, water pump, etc). Now it's bolted up to a C4 with too low a stall speed for the combo...but I have a T5 that was bolted up to the 5.0 and most the parts to swap it in.

Now for my rear gear question:
I have an 8" with 3.00:1 open diff. I can have my whole rear axle rebuilt with trac-low, new ring and pinion set, bearing, etc. For $550. I'm on the fence 3.55:1 or 3.80:1?

Don't tell me 3.73 unless you know who makes em for an 8" my guy says that's not available for the 8" even though that would be the best ratio if I swap an 8.8, but I'm not.

The car will be street driven and occasional highway and are speed limit in MI is going up to 75, which means traffic will move about 80.

 

[RaggedGT]

Warmed up 5.0 with a C4 should perform well with 3.55's. Should be fun from a launch,and won't be wound out on the highway

 

[Nosub4cid1966]

I'm leaning to 3.55, I know with the c4 that it would probably be my best option. However, I need another 500-800 rpm on the stall speed of my converter to keep the c4...it will cost less to get the rest of stuff for 5 speed swap. I just am getting opinions if 3.80 would be better with T5. I know I'll see more improvement going from 3.00 to 3.55 than 3.55 to 3.80. If it was just a road race car and 5 speed was already in, yeah i probably would go 3.80. BUT on the stree will it make that much difference at a stop light or getting on the highway?

 

[horse sence]

3:55s for the five speed

 

[rhutt]

My '66 Fastback 302 with T5Z runs 3.55's. At 70 is cruises at about 2100 rpm. Perfect balance between street and highway gearing.

 

[tos]

I'd say 3.55 as well. I'm running 3.73 with a ford racing t5 and its wound up pretty good at 65/70. Its fun around town though with this setup but if you're going to be going 80 for any period of time i'd say 3.55

 

[Realmongo]

I personally would go with the 3.55.

 

[zookeeper]

I have 3.55's in my 302/T5 fastback and they're perfect for all around compromise of performance in town and speedy cruising on the freeway.

 

[jikelly]

I have 3.73 in my rear with a Tremec 3550 tranny. I have an 8" rear end. Where I got those gears I do not recall but I got them 12 years or so ago.

 

[65-Fstbk]

Ok, I have a 66 coupe with a 5.0 based motor. Nothing exotic just a 5.0 HO with HCI swap retrofitted to carburetion (front sump, water pump, etc). Now it's bolted up to a C4 with too low a stall speed for the combo...but I have a T5 that was bolted up to the 5.0 and most the parts to swap it in.

Now for my rear gear question:
I have an 8" with 3.00:1 open diff. I can have my whole rear axle rebuilt with trac-low, new ring and pinion set, bearing, etc. For $550. I'm on the fence 3.55:1 or 3.80:1?

Don't tell me 3.73 unless you know who makes em for an 8" my guy says that's not available for the 8" even though that would be the best ratio if I swap an 8.8, but I'm not.

The car will be street driven and occasional highway and are speed limit in MI is going up to 75, which means traffic will move about 80.

I like that price for the rear. I've got the same set-up in mine. Block is a 1987 5.0HO converted to carb. Alum heads, hi rise manifold, cam etc. My rear is also an 8" and I have a T5 in the car. Haven't changed the diff yet but I really like that price you got, wish I could find the same around here. BTW - I am also going to run 3:55's in mine.
Good luck!!!