some Worldcat.org searching about Marcel Rubin reveals a few things of possible interest.
There's a 1975 book "Marcel Rubin: eine studie" by Hartmut Krones. (Perhaps a worklist? Perhaps even a list of broadcast and commercial recordings by 1975? Haven't seen it.) Also I see listed somewhere a 1995 CD with his 10th symphony, probably no longer available?? (on Ges. zur Förderung Österr. Musik) and other works also (piano sonata 1, Bach-Choral-variations, etc.) Also the 3rd symphony on a 1960s LP conducted by I think Maerzendorfer, the 8th symphony (Otvos' recording apparently) on a 1980s Preiser LP, the 5th symphony on a 1960s Amadeo LP, the 4th symphony (Rapf conducting it seems? 1980s Preiser LP) , Pastorale for strings (Preiser LP, Jan Stych conducting), symphony 1 just mentioned (Preiser LP SPR 130, Zeitgenössische österreichische Musik, 14, 1970s); other recordings also listed on other mostly LPs (a few CDs too I think.)