340 with som problems

ok now i have checked most things, compresion was fine on all cylinders it had 135psi solidly on them all, dont realy know if that is good but its defetly a sign that there isnt any big damages inside any of the cylinders..
after changing those crappy pushrods it is alot less strange sounds going on,
and the missfiring drives mee nuts its ok now i found that all the posts in my distributor had coroded and the where green some quick sanding made them shiney and i also changed all my sparkplugs just for the fun of it (delco R43xls)
and it now runs nice and strong again.... my theory at this point is that the sparkplug that was white and shiny was like that because it may not have fired at all under seirtan loads because of something gone wrong inside it, and that may have made it cleaned by those big quantitys of unburnt fuel going thru that cylinder wish i also gues is that that unburnt fuel ignited in my exhaust when it came into my headercolectors where it is hotter? difficult to say if iam right but it is my theory right now..
engine also pulls the usual 5" hg idelvacum in gear now;)


does 135 psi seam somewhat good turning the engine over with the starter with throtle plates wide open?
i know it has a pretty big rollercam that bleads of preasure at low rpm
thanks for all the input guys!