[Tomahawk30]

I just installed a 2003 5.3l from a Silverado in my 79 Silverado, and the easiest way to do it is to buy the hub adapter and use the stock LS flexplate. Then you just use standard torque converter bolts. The only thing you may have to do is open the mounting holes up a little on the flexplate. I didn't have to on mine because it'd already been mated to a TH400 when I bought it. You may also have to trim outer ear on the th350 depending on which exhaust manifolds / headers you use. I used the cheap headers they sell on ebay for swaps and had to trim the passenger side slightly.

https://www.amazon.com/Torque-Conver...4P4QWQ6WEVZZN6