I have hit a road block with my 5.3 swap

[Super73]

Do you have a scanner like hptuners or efilive that will show you sensor info in real time?

I once had a similar issue and saw on the scanner my TPS went haywire.had fuel, had spark but did not fire.

Double check cam sensor as well.. they will run with out it, but it can make it real hard to start with out it.

Also, pull a valve cover and confirm you did not loose a timing chain.