Dumb question, are they the same as Turbo 350 speedo gears? I know Turbo 400 speedo gears are much larger.

I am no expert on these but I think they could be. I installed new 3:73 gears from a 3:08 and the speedometer @ 60 mph is actually only 47 mph.
28" 255/65/15 tire on a 7" rim. If I can get a range of gears I should be able to zero in on the correct one.

Are you aware you can still order them from the dealer Chris?

3987919 19 tooth
3987920 20 tooth
3987921 21 tooth
3860345 22 tooth
3860346 23 tooth

What gear to you have now?

I did not know that, thank you Carl. I will call our local dealer.

Probably available at Napa and rockauto, same as a powerglide, Saginaw, Muncie, t350, as far as I know. There is a calculator on line maybe where you can enter your tire size, etc

Thanks Don.