Will 95 5.7 work in my 99 suburban
If your 99 has a 5.7 it may but the electronics are going to be the big challenge.
They both are 5.7 but the 99 is vortec not sure about 95. Would I just have to change heads and intake and switch sensors and use harness on 99 and be fine
Yes, that is what you would have to do. But I went the other way, built a '97 Vortec and put it in my '95 Silverado. The only problem is the block is different for the lifters, and you need the 3 bolt hole in the middle of the valley to hold a push rod guide for the Vortec heads to work on that '95 block. Now when I tore my '95 5.7L intake off, it had the Vortec block. The 5.7L Vortec cam out in 1996. So that is what you would have to look for in the '95 block. If it has the bolt holes in the center of the valley and it looks like the lifters that are in there are sunken into the lifter bores, then you can switch the top of the motor, heads and intake so you have the same set up originally. You would have to buy new lifters for a 1996 and up 5.7L engine.