I have a 2003 Silverado 2500HD ext cab and am wondering what my wheel base is. can N E one help me out? Thank You.

Welcome to the group.
I have a couple of suggestions for you, so you don't piss people off.

Always use the search function before asking a question. A lot of questions have been asked a hundred times.

Don't double post, like you have done. It gets very confusing reading two conversations on the same subject.

Fill out your signature, So everyone knows what type of truck you have. In this case you forgot to let us know what bed you have.

But we are all here to help each other out.

Regular cab 133"
ECSB 143.5"
ECLB 157.5"
CCSB 153"
CCLB 167"

http://media.gm.com/division/2003_prodinfo/03_chevrolet/03_silverado_hd/03_Chevy_Silverado%20Heavy%20Duty.pdf