Starter 12v or 6 v

have 12 volt system on my Farmall M. Starter needs to be replaced. Question is part store thinks the 6volt starter is ok. Is it or do i need a 12 volt starter? Please let me know need to pick it up today for daughters bday haywagon ride.

What's wrong with the 12V starter? Can you get by with new brushes and bushings? They sell kits for them, and or you should have a shop nearby that will rebuild it for you.

Gordo

So odd reason not getting spark anougher issue but cranking over it stopped and now it just locked up smokes, stinks, Where could I get a kit and how hard to fix or just take it to a shop

So odd reason not getting spark anougher issue but cranking over it stopped and now it just locked up smokes, stinks, Where could I get a kit and how hard to fix or just take it to a shop

The 6 volt will be just fine, unless your motor is so tight that it barely turns over with 12V. The reason is that the 6V unit will be running closer to it's stall current at 6V, and pulling more amps at 6V than at 12V. At 12V it's spinning fast enough that the current draw is lower than at 6V.

Considerations!!!
First, it probably is a 6 volt statrer on it now. Few were/are changed when going to 12 volt battery charging system and lights. They work for as many starts as a 12 volt even when used on 12 volts. Getting a 6 volt will be just fine.
The starter you have might be stuck in the flywheel's ring gear, and smokes because you tried to make it go any way. (no disrespect, but a stuck, or inoperative starter should not be smoke tested. If it is not turning at the first application of current, it will not turn, and should be repaired.
The starters on letter series (and other tractors) were prone to jambing into the ring gear and locking. IH and others have a replacement "clutch style" pinion that eliminates this issue. If it happens, the starter will not turn. To make it go, one unbolts the starter and it makes a loud click and when tightened back in, will be usable for many additional starts before it needs it again. But once it starts doing it it will continue. Putting the tractor in high gear, and rocking it hard by hand on the top of the rear wheels (forward and back, clutch out) will often snap it loose. The engine fan will move an inch or so when it is free, and not move at all when it is locked
If your starter has progressively gotten slower over a period of time, it may be dragging internally from worn bushings. This will cause massive starter overheating, and is not fixed even temporarily by loosening, or rocking. It can be easily and cheaply repaired if you don't let the smoke out of it. Which you may have done. I hope this helps, JimN

Take it to a starter repar shop
they can rebuild it for half what a new one cost.
ben there done that !!!!!!!!!!!