I'll take a picture of what I get for the "Corvette" servo, "bought it off of Amazon for $13.00 shipped and my old one. I already know it's bigger because mine is 1995 transmission. In the later 2000s year 4L60e transmissions they all started getting the corvette servo size put in all of them. Just researched it, so that is probably why you didn't see a difference. I am attaching a picture for you of all the 4L60E 2-4 Servo Sizes from GM, since you have helped my friend..

Reading you don't want to big of 2nd apply servo, so the best all around listed on the internet is the Sonnex brand.

Since I have so much play in my old 4th servo/2-4 servo cover, I am going to put in a new 4th gear servo, probably a:
Superior GM 700R4 4L60E 4L65E Billet Super Servo 4th Gear Apply Piston & Cover Overdrive 700-R4 4L60, they are alot cheaper on Ebay.

I also have a never used T700 4th B&M billet super servo that's at my dad's house I'm going to go get tonight. I bought it for my old 1983 Camaro 20+ years ago and never used it, so if it works I may use that! I think I know exactly where it is after all this time :-)

 

Corvette servo piston is perfect for a V8 blazer but I think it will hit the band too hard when behind a V6. Just my experance. A correctly tuned trans is 'ballanced'.