i have 550W Rhino RX-550PA, 6pin PCIE/12cm fan/Sleeve /black (CWT) is it be enough for r9 270 (non x ) and fx 8320 ? and with AM3+ 760G Gigabyte GA-78LMT-S2P mobo ?
Should be enough. The R9 270X (I know you said Non-X, but the X is slightly more demanding so it gives you a good benchmark) requires 24A on the +12V rail and a 500W PSU minimum. The Rhino RX-550PA delivers at least 26A on the +12V1 rail, and 23A on the +12V2 rail. You should have plenty of power for the non-X R9 270.
I know its not a good power suply but i will use it just for few monts till i buy 600w lc power psu is it be good for 3,4 months ? and yes will this mobo AM3+ 760G Gigabyte GA-78LMT-S2P be good for fx 8320 ?