Here’s a list of Perks to select from levels 31 to 40 with the Best Power Armor Build Guide in Fallout 4:
Level 31 – Gun Nut 3
Level 32 – Demolition Expert 3
Level 33 – Bloody Mess
Level 34 – Demolition Expert 4
Level 35 – Heavy Gunner 4
Level 36 – Medic 2
Level 37 – Bloody Mess 2
Level 38 – Save
Level 39 – Gun Nut 4 + Armorer 4
Level 40 – Chemist 2