If you get or have guages and use a box on the lower settings you should not need transmission upgrades as these 48RE's are alot stouter than the 47RE you had in your 99. If your going to use a box or programmer on the upper settings then talk to this guy www.gbtransmissions.com He is very knowledgeable and trustworthy and honest. Will not sell you anything more than you really need. Just click on the link to go to his website. Oh and he is a sponsor, he has an ad in the TDR magazine. If your going to do any power upgrade and tow, get guages.