Helping a friend start in Trad with an old Pearson recurve

[highpoint forge]

Looks like a knockoff of a PTF widow but it's old and has a really pretty wood riser section actually, cream colored and brownish limbs. 40#@28, 60amo. He nabbed it at a garage sale for $20. So he needs a string. I'm assuming B50. What length should it be and such? I told him to call 3 Rivers....any recommendations so he doesn't blow this bow up? We are going to learn how to tune arrows next, and not buy what looks good at Academy!

[Bear Heart]

56"  b50 string

[highpoint forge]

Thanks!!