How much smaller of a belt do I need for a 3.8 to a 3.3 pulley drop?

[tweeder]

I have a different configuration and different idler pulley for better wrap so the standard belt sizes won't do. Imam using a gatorback 4050665 belt now on my stock pulley as well as the 3.5 which is on there now. I have a 3.3 on the shelf waiting to go on but I want to order a smaller belt to keep everything tight. I think how the gatorback numbers go is the 665=66.5".

 

[Russosaur]

According to the safely modding your 3800 thread....

658 - GTP/GS/SS supercharged with 3.2 - 3.5" pulley (66 3/8" - 1687mm)

Edit: i missed the different config part. I'm assuming its one off an H body car like a bonnie my bad. That size i posted isn't right then probably.
Sent from BFE

 

[blownGP]

I'm running the stock belt in.my 3.5 j bought the shorter one and it was too tight for my liking

 

[tweeder]

i want it as tight as possible to eliminate belt slippage.

 

[REDCRAPGP]

i want it as tight as possible

Lmao don't we all