Number one problem when a GM starter just clicks and doesn't turn over is the solenoid. Number two problem when that happens is bad brushes. If you can rap the starter with a hammer and it cranks over, suspect it needs brushes. A jumper wire will cover up a lot of sins by delivering more voltage which just covers up the problem, but doesn't solve it. Either way, I'd rebuild the original starter if you want reliabilty, since many parts store rebuilds are carp. Another solution is replacing the old starter with a brand new super small PMGR starter. There are many later model cars that use them and older cars can be retrofitted, especially if the car or truck in question has a HEI distributor. The PMGR starters usually require different starter specific bolts, due to the starter having metric size mounting holes and the block having US spec threads. Some starters come with the needed bolts, some don't. Number of teeth on flywheel/flexplate determines whether a straight across or angled bolt pattern is used. Here's a PDF on Remy starters that can be interchanged.

Linky -->PMGR Remy Chevrolet starter info.

A 1970 Monte Carlo came with points, and a PMGR starter that has the "R" terminal would be needed. If the distributor has been replaced with an HEI, the "R" terminal on the starter is not needed.