Hello. I'm very new to tuning but I'm learning to help fine tune my car and hopefully future projects. I have a 1972 Cutlass with a LS1 and 4L60E from a 2000 Corvette. The transmission now has the internals of the Corvette, but I swapped the case to a Camaro style case for a dipstick tube hole. The input shaft is from a 04 Silverado, so the shaft seals inside the torque converter. I'm not sure if the output shaft was done previously but it has an output shaft with a 40-tooth gear and a VSS on a tail shaft housing. I had a 2600-2800 stall TCI breakaway torque converter when I had the vehicle dyno tuned in 2015. I just changed my converter to a 3200-3400 stall Circle D converter. I have a few issues that I'm dealing with that include the delayed/rev-limiter on full throttle 2-3 shifts, and TCC surging around 40-50 at steady cruise. I've watched videos and read forums about changing the WOT shifts lower in speed and RPM. That seems to help some, but I don't have it perfect yet. Someone had said that the surging of converter locking and unlocking can be changed by either no having your converter lock or have it lock only at higher speeds. Now to my main question which will help me dial in the other concerns. Since I changed my converter, I downloaded Bluecat Transmission tool to help change my trans tunes easier after trying to do the WOT shift changes by lowering shift speeds and rpms. So, I've found out what my head scratcher is with using Bluecat and just using the Gear/Tire Wizard to help change my Speedo settings and comparing it to my OG tune. Now my OG tune did only have a slight difference in tire height when I had it dyno tuned, but not enough to change it to what is happening now. I have 3.73 gears, 40 teeth on my VSS Gear. Tires are 275/40R17 which come out to 25.7 diameter and 786 revs/mile. My OG tune speed was only a few MPH's off of GPS MPH. I used the Compare Function on my OG tune and the Bluecat tune. I see they used 45 teeth instead of 40. Using that, I still don't know how that got the VSS Pulses Per Miles they used. With the Bluecat tune, it will say I'm going over 158 MPH at 50-60 MPH. I changed the VSS PPM multiple times using the Gear/Tire Wizard and can't get close to their numbers. Can anyone tell me how they might've come up with their numbers of 225,000 to my 117,086? I did do multiple renditions that included changing the VSS PPM to what my OG tune had. It seemed to show close to the correct vehicle speed. Not sure if I should keep their numbers but it might be off since they have 45 tooth count set.