Not lazy at all, and the 360 motor home heads are more than likely a set of 475 castings without the exhaust air injection ports drilled. Fairly common on truck engines. I would just run a compression test to see where things are at but I expect zero problems if the engine has been stored properly to prevent any stuck rings. The Rumblefish plan is as good as it gets here, I think you'd be surprised enough by the outcome that your 340 build would fall on the back burner with the "someday" projects.