305 mystery problems

hey its my first post i just found this site not long ago, im waiting on a wiring harness to do a tpi swap on my mighty 305 but i desperatly need to fix some mystery problems that have been driving me NUTS.

-oil not just leaking, but spewing out of the pass. valve cover during a highspeed run, ie. above 4000rpms for aprox 20 secs, im using decently thick GM stamped steel covers, ive tried reg cork gaskets, thick cork gaskets, rubber gaskets, rubber gaskets w/ steel inserts, and theyll be nice for a little while, then one morning ill notice a nice sized puddle under the car, and sure enough oil EVERYWHERE, itll make you crazy trust me, when i think logically it must be a pressure build up of some sort to force oil out, but its got a breather, and yes air still passes through the breather i found out the tasty way

-mystery problem 2: coolant loss, about a gallon a week, no signs of anything under the hood, pressure tested the system, not a leak anywhere, cap tested good as well, no smoke from tailpipes at all, though it was the intake manifold, replaced that gasket, same problem, though it was head gaskets, replaced those, no luck (also had heads magnafulxed), interrogated antifreeze fairy, no luck

i'm at a loss with whats goin on, possibly both problems have a common source but i just dont know, and yes i know i know why bother with a 305, but i dont have the money to rebuild my 350 just yet (M3932388 HH block, 3947041 heads)

enlcosed is a pic of my baby to hopefully invoke some sympathy