Overdrive for a 1976 GMC C15 suburban with a 454

[nm78bronco]

Hello All,

I'm really interested in getting an overdrive for my 1976 GMC C15 suburban with a 454 engine.

Currently, I have a TH400, 12-bolt with a 3.07 ratio. I recently purchased a NOS 3.73 12 bolts gears on ebay for installation.

My truck will be primarily for day trips and around town (no towing), however, I plan to tow up to an 8000 lb trailer, up to 10 times per year.

The 2 options I'm considering are:
1) gear vendors overdrive
2) 700R4 OD

My dilemma about the gear vendors is I keep hearing about unwanted drive train vibrations which I want to completely avoid. Does anyone know of an excellent gear vendors installer in Arizona, who successfully installed a gear vendors in their truck with no vibrations? I really want the the truck to be vibration-free like the factory.

From what I've read, the 700R4 can be built to do what I want if driven intelligently. It lacks the gear splitting of the gear vendors which is a major minus, however, again, no vibrations is very important to me since the vehicle will be doing alot of highway driving. I'd need to install a huge auxillary transmission cooler for this treanny. Did the factory have auxillary transmission coolers for the tow package trucks?

Thanks for any comments