You're looking at $1000+ to run a carb - as the previous poster added - that point it's not too bad to just keep the EFI thats already there and get the benefits of it.
I thought about running a sniper or fitech on my 6.1 but again, the cost. I ran a factory PCM style computer for a while but I am currently working on an MS3X to run it - for... future modifications.
I have <$800 into my MS3X and it'll run the entire engine with spark, fuel, allow for tuning and is not proprietary in any way - so it can always be expanded and modified for the future.