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What would be the best transmission for a car with a 375hp/425ft engine and 3.73 gears that will be driven on the street and interstate?
 
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with that kind of power i personally wouldnt even consider an auto. manuals are way too much fun. if youre building that kind of engine and running those gears you cant be worried about mileage and your engine should be just fine running high rpms. of course if you can afford it i think summit sells a richmond six speed for smallblock fords. thats the only tranny i would ever consider for a street car. but since i cant afford one i happily bang through the four on my toploader. just my opinion though
 

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I have a C-4 that is so unmodified it scares me behind a 392W. Going on two years, no problems.

Interstate driving is not that much of a problem with a 1/1 transmission and lo gears. If you insist on running 80 or 90 with everybody else, your motor will be buzzing! All you have to do to live with lo gears is drop your cruising speed a little.
 

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In my '68 with a well built 351W the first C-4 blew while on the test drive from the tranny shop. I am not sure what it was other than a lot of smoke and no more tranny. The second version they used the stronger pieces from later versions of the C-4 and worked fine until I sold the car. The best traction aid was a sometimes unwilling fat person in the back seat.

I have a toploader in my convertible. I wish instead of spending $600 to rebuild the toploader I had purchased a short shaft Tremec 3550 for the lower first gear and overdrive 5th gear. The vert has 3.25:1 rear gears and revs a little over 3,000 RPM at 70 MPH. Local freeway speeds sometimes exceeds 75 and even 80 MPH.
 

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If you want an auto, any would work. A C4 will sap up the least HP from that 351. I ran mid 12's in my 70 coupe with a 351w, c4, 411 gears, and 9 inch slicks. Only mods to the trans was a rebuild, and a shift kit. Worked well.
 
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