i,d wash it all down with some coca cola and a wire scrub brush,. then look closely to see whats deep pitted or not,.,. the bottom end looks furry, i might remove the rear main cap and wash it with some acid,. where the oil pump gallery is,.
Go after everything with some hydrochloric acid fairly weak solution,.and wire brush
hose it all off really well with the garden hose,. use an air line to blowit all dry or a hair dryer,. then inspect it,. use some steel wool on the bores with wd40 to see what you've got,. wash everything off good with the hose again and dry and oil,. heads don't look too bad,. a rough head surface makes for a good gasket seal anyway,.
i am assuming you will be smart enough to take necessary steps to protect yourself when handling the acid, right?
1999 chev suburban C2500
300,000 mi