Why not do a 5.7L engine swap instead? This is an extremely popular thing with Astros, which by the way also use the 4.3L Vortec and a 4L60E automatic transmission. That said, I would think your standard transmission would likely be a direct bolt on swap as well, given that the 4.3L Vortec is usually married to 4L60E trannies in smaller trucks, and the 5.7L Vortec is a direct bolt on swap for those...

It's worth looking into. Although I'm sure it does okay, that 4.3 has got to be under some strain pushing 1/2 ton truck around. You may actually get better milage. Many Astro swaps report this as well...

Edit: You will need the computer from the donor vehicle, and given that it's a 99 truck, you'll also want to try to ensure that it's the same year. You'll get a lot of help from Chevy Astro forums on this one actually--pm me for details if you want. But I'm sure there are folks out there who have done this with Silverado work trucks...

 

i have thought of an engine swap but the thing is i dont know much of engine swaping and choosing and engine i need some1 to help me out. i would love having a 5.7 on my chevy no doubt. how much do you think it would cost to do a swap?.. so you think the engine just fits in perfectly i wouldnt have to get a new transmission to handle the 5.7? thanks alot for your help.

 

I too would recommend 5.7 L engine, itsa good choice