How much oil?

[f.monroe]

I replaced the complete A/C system except the condenser on my 77 in March. The compressor went south and I am going to do it again . I hope someone has a spec book that tells how much refrigerant oil to use in each component and what the entire system holds . I would like to know . I added the amount of oil that the parts store suggested last time and it either wasnt enough or the compressor was just junk .Pick one , but I would like to know what you guys suggest . Also , is the $20 variable orrifice tube worth the money in a R134 converted system or will the $2 OT work just fine ? Thanks. Frank