5.2 front crankshaft/timing cover seal.
I was wondering what the difference in the repair sleeves is. The one I was told it called for is National 99128 but then I seen where there is a National harmonic balancer repair sleeve 88218. Which do I need when replacing crankshaft seal 71303?

 

Rock Auto shows National part number 99218 for your harmonic balancer repair sleeve kit.

Given that your truck/motor is about 20 years old, I'd suggest replacing or rebuilding the balancer with a new one instead of trying to repair it with a sleeve. I've once used these folks several years ago and they did a great job on rebuilding a 225 /6 balancer for me - https://www.damperdoctor.com/

 

I have not started to replace it yet I don't even know if I need the repair sleeve I just want to get everything I might need just in case

 

The seal that comes in the kit with the sleeve, won't work without the sleeve. It'll be too loose, and leak.

Replace the balancer, if you don't want to have to worry about not having the right parts. Then just pick up a stock seal, and you'll be golden.

I have never had any success with the repair sleeves, they always wrinkle on installation, and thus, will never seal.....