cool. its best to have a machine shop take care of it for you. the bore needs to be perfectly inline and true.
If you are asking about the fit in the axle itself, as your title suggests, it should be a nice tight fit on a new axle. A light "tap" fit is OK. Is there any paint, coatings, or even light rust in the bores, if so, it should be sanded out. If it still doesn't feel right, try your new pins from the top and bottom on both ends and see what's what. It would seem odd if both sides of the axle were out of spec; but who knows where and how the new axle was machined.
Did you get the pins from So Cal as well? If 'yes' then the pin should slide smoothly in and out from either end and it'll be obvious that it is precise machined fit, no slop, nothing. If it is tight in the bore then the locating pin that locks it in place won't be able to seat right.
I recently assembled a front end with a new So Cal axle and it surprised me how tight a fit the king pins were. As someone said they are usually a nice slide in fit. They did go in with light tapping after a good clean out.
The pin should fit in the axle and fall in under its own weight with out force help or any excessive slop, the lock pin takes over from there and forces it to the side of the bore. You don't want it to walk around, click or wiggle but it shouldn't need force. In the spindle it should fit tight enough that it's own weight isn't enough to let it fall thru. Two thumbs pressure to push it in and the same to push it back up. Maybe 3 thumbs. Should not need hammers,
I’ve had the same problem with my So Cal axle. Had to send it back, as they had forgotten to finish machine the holes. No complaints from the customer service end, they were real good and even paid for the shipping both ways. Sent from my iPhone using H.A.M.B.
A jerk machinist here in Atwater looked in the book, then reamed my first spindle on the Sunnen machine to 'specs'. The minute he handed it to me, the new pin was 'sloppy'... Dumb shit said, "Ah weunt accordin to th' BOOK..." I paid him $10.00 for the one, should have thumped his melon. An old gent sold me 20 king pin bushings for $30, (N.O.S.) so I'll ream them myself, by hand, with my good old WILSON Ford king pin reamer. Grrrrr.....
I've used and sold dozens of So-Cal axles with no kingpin problems, just a light coat of white grease and they slipped right in. More recently I had one for a personal project and the king pin would just start on one side and I didn't want to force it so I had to use a brake hone for a few minutes in that side to get a slip fit. On the other side the fit was great
^^^^^ you would think that as much as their axles cost you shouldn't need to do anything but put it together. Quality control is becoming a thing of the past.