Farmall H tractor 6 volt starting with 12 volt will be problem?

can you crank start? you can use 12v to start but it could burn up the starter if it over heat the windings with to much cranking I have a old case and i alway do a cold start with 12v then use the built in crank because it starts easy when hot I use jumper cables because drops the voltage a bit closer to 6v but it really spins the engine nice , have you tried a brand new 6v maybe your battery is old as for the plow you can always fine antique stuff online not sure if H has 3 point hitch but if seen adapter equipment that converts it to 3 point