A guy I have bought several surplus rifles from (and for very good prices) just sent me a message letting me know he's getting rid of a Springfield 1903. He says it has the pistol grip stock (I'm assuming a type C stock). He says its an arsenal rebuild and the barrel is marked USMC 1943 with a small "s" under the date. He's asking 600. I've learned a bit about 1903a3's (because of a few mistakes) and was wondering if anyone knew anything to look out for. I don't mind if its been through a rebuild, as long as its not something someone pieced together with parts that they never put together. I've read that Type C stocks were put on 1903's in 1942. I'm going to ask what the serial number range is to make sure its not one of the low ones.

Edited - receiver is Remington

Thanks for your help

Remington didn't make '03s until 1941, so that one was rebuilt at some point either during the war or shortly after. No Remingtons are low-number receivers; they were all heat-treated properly.

Assuming good condition, $600 is a good price, I'd say.

The USMC barrel is obviously a replacement barrel.  Sedgley barrels can be good barrels.  There is a good probability that the USMC barrel was not put on as an arsenal rebuild.  It could have been but most of the 1943 and 1944 Sedgely barrels were sold as surplus and not used in government arsenal rebuilds.  If the USMC installed the barrel then you would want to look of vice marks on the barrel under the forearm.  Also possible a large punch mark in front of the serial number. Some of the 1943 and 44 Sedgely barrels were scraped, being bend, then sold as scrap with some enterprising individuals buying the barrels and re straightening them and then selling them.  I have had 2 USMC 1944 barrels on rifles and neither one was bend an both gauged as new.
All of that being said.  If the barrel is good and straight and the stock is a USGI C stock with any cartouches then $600 is a very good deal.  
Do you know what month the barrel is dated?  What is the serial number of the Remington receiver, early or late production?  All milled parts or some stamped parts?
And really, no matter what the answer to all the questions are, if the barrel is straight and there are no extra holes in the receiver then $600 is a good price for a good condition 1903?