The '06 and newer engines are the better ones to start with, especially if using stock EFI setup as they have the MAF trim on them. Again, nice project efi-diy.
As you stated, the engines are fairly reasonable. However my path of manual transmission would cost a minimum of $2500 for the driveline complete without the mods to the oil pan yet.
To all - Based on my research, the trans mounting pattern on the ATLAS engines is NOT anywhere near the SBC or even the GM 60 degree. Either custom adapters are required or use parts from the Colorado 3.5 for a manual transmission with a custom flywheel for the 4.2, or stick with the 4l60E from behind the 4.2.
Hot Rod Dad, There are plenty of ways to make the 6B or even the 4B a little quieter. The 6B is easier than the 4B because the 4-cylinder shakes like a dog passing a peach pit and the whole truck will vibrate. For a 6B, get a 2005 or newer ISB with multiple injections per cylinder event to pass the Wendy's Test (Pulling up to a Wendy's and ordering food without shutting off the engine). If using an older unit, wrap the exhaust, and get your hands on the old NP options which dampened noise significantly. If the engine you use has the Bosch In-line pump on it, insulate the pump, this is where half the noise comes from.
If you need a 2005 or newer ISB I think we still have some takeouts at work
Scott
