Just because you are asking and you have a M98 receiver and a M48 barrel I suggest you install the bolt in the (standard length) receiver, then install the M48 barrel. If the barrel stops before the shoulder at the end of the shank threads contacts the receiver ring measure the gap between the receiver and barrel seating surface with a feeler gage, then remove the bolt and continue screwing the barrel into the receiver. If the barrel screws into the receiver to within a few thousandths the thickness of the gap will indicate the amount of of metal that must be removed from the M48 barrel face.
I do not have less than 30 Mauser barrels, to most that would be a ‘can not miss’ when setting the length of the chamber, problem, finding a Mauser barrel with +/- case head protrusion, my barrels have .110 case head protrusion +/- very little. I purchased 4 Surplus Mausers that were sold as being suspect, I used one barrel, 4 bolts and the 4 receivers to test the rifles for ‘suspect’, the difference in chamber length of the 4 receivers, 4 bolts and 1 barrel was .001 thousandths., the suspect rifles had worn out 2 barrels before I became the proud owner.
There are two seating surfaces on the 98, one is between the barrel face and ‘C’ ring/torque/seating surface, the other is on the face of the receiver ring, the seating surface on the front of the receiver ring contacts the seating surface at the end of the threads on the barrel shank, it is important the last contact to be made when securing the barrel is on the front receiver ring. For those that have never took up the ‘feeler gage’ as a transfer/standard/verifier can use depth micrometers, etc.. When the barrel bottoms out I check the gap between the receiver and barrel, contact is made on the front receiver ring when the slack is removed between the threads and crush takes place.
It is not a matter of ‘HOW’ but ‘WHY’, as someone said “get a gook”, I ran off a few copies of barrel instillation instructions for a friend, the instructions were ‘BI’, before the Internet, I do not shoot gages, I shoot ammo, I determine the length of the chamber first, If I felt is was absolutely necessary to have a ‘head space gage’ I would make one. Again, I modify go-gages to go from go-to infinity gages, nothing more useless than a gage that everyone should know, when chambered, will allow the bolt to close. My favorite gages measure in thousandths from .000 ‘zero’ to infinity, when checking chamber length infinity would be a practice .016 thousandths.
The instructions gave options and were from the manufacturer of the barrels.
If you have a bolt for the 98 remove the extractor when determining bolt face/barrel face clearance, the extractor will hit the flat of the M48 first. The M1917 and 03 Springfields have extractor cuts to accommodate the cone face barrel.