360 build.

if it's not the stem seal then it's the rings
new seals should even seal bad guides- for a while
do a leak down test
I can't remember the thread but if this is just a temporary motor till you build a 360 you can take it apart and clean gently remove the ridge, hone, knurl the pistons and slap on a set of cheap rings -depending on what you find when you mic the bores
if those are KB pistons remember to set the ring gaps for those pistons
you could also move the rotating assembly to a different block and save the cost of pistons
but you would have to bore the new block for these pistons
that compression is way off for those pistons and it will never run right with that much oil
was this balanced or do you know
if the plugs are fouling and you have to limp it along for awhile try Champion RFN14LYC or
Champion 82 Spark Plug RFN14LY