Welcome to the forum. I am going to swap a LS1 this summer in my full size 1981 GMC. Although I perfer the LS1 another good swap is the LT1. It uses the older style 350 block but has multiport fuel injection not TBI and it is quite a bit cheaper that the LS1. It will also bolt into your truck with less modifications that the LS1. The down sides are the LT1 has less stock horse power and gets less fuel mileage that the LS1. Just a thought!! 
2006 Superior Blue Trailblazer SS AWD, Stock as a rock
Sold: 2002 GMC Sportside Denali front end with a 2002 LS1, FLT level 5, Yank 2600, Trick Turbo, T76, Nelson intercooler, 60LB injectors, Warbro fuel pump, Eaton locker, Magnaflow, 3.42, Nelson Performance Tuning (speed density).
Sold: 1981 GMC LB RC 1500 2002 4.8L 4L60E 12 bolt 3.73 Richmond Lock Right AC PS Nelson Performance tuning
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