I would take the valve covers off and see if it has the adjustable rockers and then take the cylinder heads off and verify the bore and stroke and deck hieghts, if it is the orginal truck motor it will have those real heavy valves that where never intended to rev past 3500 RPM so I would replace them with new stainless 11/32 stem valves and maybe increase the size of the valves at the same time As far as the pistons I'm sure there cast and probally really low compression, so is your freind feeling lucky on using the cast pistons with a blower? If the bore is straight and round I might be tempted to try running those pistons with a decent set of new rings and 7 lbs or less pressure IHTHs BTW, don't be suprised if those pistons have 4 rings on them that are impossible to find now