John,
Your donor solenoid style starter might have a different pinion configuration and could complicate any starting issues you have right now.
I would stick with what you have. Clean the cables, charge the battery, check plugs and timing... generally just get things tuned and it should go. The worst case scenario would be pulling the existing starter, cleaning the commutator and maybe installing new brushes. Even jumping the existing setup might help wake the beast up.
Stuart
