I have been using a very old pearson recurve #40.
Over the years of storage it lost some strength and I shot Beman 500 (7.3gpi) at 29 inches with a 100 grn head.
I just got a new Martin recurve #50 28 inch draw.
Can I use the same arrows and just increase there weight by using a 125 grn or heavier head or should I just get new arrows? Or will these do fine as is?
No one can tell it is going to work. You need to try it out and make adjustments as needed. I seriously doubt that a 25gr change in point weight will make that much difference with 10# change in draw weight, or more. I think you will need to make some bigger changes then that. But like I said, no one can say, you just need to try some things out. Sorry it isn't as easy as just saying yea sure.