I have this 98 Mauser, it had been sporterized, meaning it has been scrubbed of nearly all markings that will give it a manufacture date. As close as I came get is 1940 to 1948. what I'm trying to do is determine from testing different powders, just what max pressure limits I should be using as a guideline for this rifle. Can someone point me in the right direction on this. I just don't want to pick powders with load pressures that will exceed what this rifle was designed for. Thanks!

Give me all the markings that are on it. Very few Mausers were made from 45-48. I have seen them built into belted mags that operate at 55k psi with no problems and I have seen 30-06s with lugs badly set back. Need more info on it. You can always have it re hardened. Does it have a barrel on it now and what caliber is it?

It has the barrel on it that it came with and it is in 30-06. It was pretty messed up though, the rifling is really good, but it had to be pulled because it was severely out of headspace. What was found were the barrel threads were all mangled and sheared, there were only one and a half threads actually doing anything. So the bad thread area was cut off, re threaded, and re-chambered. Now it head spaces perfectly, but the thing that has me concerned, is that when I took a chamber casting there is not a lot of space between the end of the chamber neck and when the rifling begins, hence my concern about the pressure issues. Here is a quick link to Flicker for the photo's of the markings.
http://flic.kr/s/aHsjJZNw1x

Nice eagle N nitro proof; are there any markings at all on the left side of the receiver wall? you have a Mauser 98k trigger guard and a Gewehr bolt stop. No need to worry about it as long as they got the threads right. Load the hell out of it.

The rest of the receiver is completely clean, I took pics of every mark on the receiver and barrel. I did take it out and fired half a dozen factory round through it to get some fire formed cases to study and measure. Thank you for your response, I feel a bit more confident about it. The powders I'm looking at for testing are R17, 4064, and 4350. I'm still a bit concerned about the rifling being so close to the chamber neck.

Will it chamber a factory load? if not you should ream it with a finish reamer to give it some throat/leade. If you shoot a factory load, how did the primer look? Those medium powders will be good; hard to get into too much trouble with them. 4350 is slow for an 06 so no problem there.
Whoever fitted your barrel should know all this or he should not be installing barrels.

If factory rounds function and fire with no issues, then the amount of leade or throat is sufficient, it would only pose a problem if the mouth of the case was being pinched in the chamber.
Seeing as though you have a chamber cast, how does the throat measure up?
Measure from the step just in front of the case mouth to the origin of the rifling, I would guess it to be between .100"-.200" in length which is in the normal range.
Your Mauser action should handle any standard 30-06 handload, and powder type doesn't make more pressure in book loads, it only changes how fast or slow it gets to that max pressure, I would recommend powders like H4350, RL19, RL22 and H4831sc. These powders perform well in 06 sized cases.

Cheers.