In my opinion, Bolens are great little tractors. The Bolens G8 denotes that it's a 8HP engine with gears. I think the engine should originally be a Tecumesh engine. Incidentally, the H denotes a hydrostatic. The G8 essentially replaced the Bolens 813 in 1973.
There are other more knowledgeable members who can provide more information than I but it certainly a good little tractor and, unlike the Wheel Horse, parts are getting harder to source but they are still out there.
Good luck!