How does what the previous builder charged have any affect on whether or not the motors are worth rebuilding or freshing up, Flattop? Thats a first for me on that one.
No reason at all your engines can't be updated and ran again as long as they are done right and are legal. If the engines were built new and only ran a few times, then just sit for a couple years, they aren't gonna be worn out beyond the point of being rebuilt. Just send them to the builder of your choice and have them updated for the current rule set, thats about all you really can do if you aren't sure they are legal now. Cam, pipe and flywheel would be my concerns if it were me pulling a couple of 2012 engines out of the dust and planning to run them again. Safe bet would be to send them to be updated unless you know how to check them for legality and know what your doing and what your looking at