If we are going to include V8 swaps in this I will throw the 5.3L Vortec/ 4L65E swap into the mix. I've done quite a few swaps in the 60 series and it's a game changer. You keep the old school cool of the 60/62 series with updated power to make it easier to drive in modern day traffic.
The HUGE reward in this swap is parts availability and overall knowledge of the platform in shops across this country and others. There are literally millions of Vortec motors out there in scrap yards sitting in wrecked GM and Chevy trucks. Both the OEM and aftermarket support of this platform is only out shined by the support for it's originator, the SBC. The Original iron block 5.3L Vortecs and their aluminum block off spring are considered to be fleet motors, capable of 300-500K miles on basic maintenance. I have an old friend that is a fleet mechanic, has been for 35 years. He tells me that hands down the 5.3L posts better numbers than any other gas motor they've dealt with.
I've swapped in the LS3 6.2L and lord knows it is cooler than he%%, but for the reliability factor and overall maintainability, the 5.3L is hard to beat.
Just one guy's opinion