Very early Ruger model 77 with the tang safety

[TAWS]

I am trying to re-barrel an earlier Ruger Model 77 with the tang safety on it. Is there any difference in the original barrel threading on the Model 77 and the later, 77 Mark I and Mark II? I know that here is an extractor cut you have to deal with on the original 77,---anything else? The rifle I have has a 23 .5 in Shaw barrel on it and is in a 280 RCBS Imp. and I want to take it to a 280 Ackley Imp., due to being unable to find the RCBS Imp. 30 Degree reamer.