Definately the OS 70 4 stroke,best torque and response,perhaps a GOOD 13x4,12x6,maybe 14x4.Try APC blades,try to use a low pitch wide blade (W)
Dont fly it fast, mid throttle at cruise,all you want when you are going up.Make sure the firewall and landing gear block are well glued or pinned or screwed.
Its outdated,but a good plane to try your skills at 3D.
Good luck,have fun