I have a '97 4X4 Suburban (454 EFI) that I pull my Tractor and boat with. I have also upgraded the features of the truck increasing the weight probably 1500 pounds or more.
I installed the Banks Kit for the engine that had headers, cool air intake etc. and it helped quite a bit. I have the 4L80e Transmission in it so I can change the tuning very quickly. All this said, like you I really have a difficult time getting the truck to go. Sooner or later I will need to go into it. (200k miles currently) When I do I think I will put a rear mounted turbo kit on it. By cleaning up the heads by matching and lightly porting them, putting some lower compression pistons in it, and a good turbo cam I don't think I will be needing a diesel. I like them, but the truck is paid for and this would be a fairly easy cost effective way to get the power I want.
My truck came from the Factory with 290 hp/410 Ft Pounds of Torque. The Banks kit gave me about 12% increase in the power, mainly through just making it breath a hell of a lot better.
The right turbo kit, I think would be the best for my application is sold through
www.ststurbo.com.
For my truck I would probably use the Universal kit. Last time I looked in it, putting it on my stock motor with nothing better on the inside, I could expect 35-40% gains in hp and Torq. That would certainly get the power where I want it without buying a new truck. The kit is about 2K complete.
There are a number of people who have had good luck with them especially with motor homes and trucks like ours.
Anyway something to look at. Let me know what you think.
I hope this has helped,
Take care,
Ty O'Neal