Hello, and welcome!
I also have a '99 1500 Suburban. This is my second 'Burb as the first rusted away thanks to New England weather and salt. both were originally equipped with 3.42's, 4L60E, and 5.7 engines. The old Suburban was built for economy and some towing. I built a 302 smallblock, short headers and duals, installed a massive transmission cooler, an OEM tow package radiator, a 2200 rpm stall converter. I was able to successfully tow large loads by using a weight distributing hitch and because my trailer has electric brakes on both axles the vehicle always stopped reasonably well. The only issue was the 302's powerband was a bit weak in 3rd at 65-70 mph. But because the engine was built well, I could drop to second gear and run rpm up as high as needed to accelerate or climb hills without problems.
The current vehicle is still running the stock 5.7 while I wait for time to swap the 302 from the other 'Burb. I have replaced the front brakes with a hybrid of parts that allows the rotors and calipers from a 2009 ish 1500. These are large enough that I had to switch to later 17" wheels. I have also replaced the stock master cylinder with an older part to delete the "quick takeup" master cylinder and get rid of the slow, slushy apply that prevents quick stops. I am also planning to build a custom rear spring pack using a mixture of the stock leaves and leaves removed from a 2007 2500HD. I am still trying to work out whether or not the "light 3/4 ton" trucks from around 93 have larger rear brakes than the stock 'Burb. I do intend to stay with the 3.42's because the old truck routinely achived 16-18 mpg during long cruises with no trailer. I would love to have a different planetary set for the trans to get rid of the 1.62 second gear ratio but I'm not sure that will happen.
As far as tuning, the later 0411 will offer tuning options and improved performance over the stock Suburban pcm. I hope to find time to switch my truck to the later pcm some day. It is possible to add a tow/haul button to the stock pcm but the pcm will need some tuning to take advantage of it. There was a chart made by Lextech / Jeff of Pacific Performance forum to help with the pcm swap. He is on this site as well. Lextech's truck was featured in a book on pcm replacements that could be handy. https://www.eficonnection.com/home/p...ontrol-systems
Feel free to start a thread about the swap. Include pictures, too. Everyone loves pictures.
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