yes..all you have to do is get oil to the rocker shafts......and if the magnum block is not drilled nor has the correct cam bearing or if the cam is not drilled for the to supply oil to the heads....
see it is pretty easy...LOL
that 73 340 probably does not make anymore hp the the magnum truck engine...and the 360 has more potential for hp then the 340...bigger is better....do the same mod to 360 as 340...360 will win..