Inline 6 drive train advice

[62 bigwindow]

I have come to the point on my 66 that I am ready to install motor and trans
to mock up ride height for the bag mounts on the rearend and have decided in order to be a little different go with a mild 250 inline 6. My question to you guys is what trans to go with and what rear end gearing? I plan to run the stock 12 bolt rear end. I was thinking of the 700r for the overdrive and ability to cruise at highway speeds. As always thanks in advance for any and all input..

[boucher racing]

I can speak from experience. I have run a stock inline 250 with 3 on tree. stock Inline 250 with T5. Built turbo'd inline 250 with T5. Built turbo'd inline 250 with 700r4. My rear end is a 3.54 gear.

The most pep was with the T5. Very little drivetrain loss. Great gear ratio spreads.

The 700r4 is the most comfortable, but does feel a bit slower about 75% of the time. The other 25% the turbo is spooled up and its a raped ape!

If the inline 250 is not making big power, I would stick with a T5. Plus, the swap is much easier and far less money. I switched just because a auto pairs well with a turbo.

Boucher'

[Lugnutz65]

It's important to match the OD gear with the rear diff. Too much OD with the wrong diff and it will not drive well in OD.

3.73 rear works well with a 0.72 OD
3.42 rear works well with a 0.86 OD
3.08 rear is hard to match with OD because it will probably cause an inline 6 to lug in OD.

I'm enthusiastic about T5s but finding one with a cable speedo S10 tailhousing is tough. If you have bucket seats then just use a Camaro tail housing with a cable speedo output - those are easy to find.

[62 bigwindow]

Sorry I did forget to mention I do want to use automatic transmission

[NEWFISHER]

My 50 burb sports a warmed over 250, 700r4 and 3:73. Gets 19 mpg with a 29" tall tire and is a great daily combo, cruising and pulls a 4000lb camp trailer a lot. I with I had 4:10s when pulling the hills with the trailer but only 20 days out of the summer I can live with the better daily feel with the 3:73s. I'm running a heated clifford intake and a Holley 390 which is super easy to run the TV cable set up for the 700r4.