I ran a Massey Ferguson 31 sicklebar (7 ft wide cut) off my 2008 Mahindra 5525.
View attachment 410004
Bought it at auction for $550. Cost about $200 in new parts to get it running.
It's belt driven. The older type is driven by a wooden pitman bar. Either type will work, but I prefer the belt drive.
If you buy a used sicklebar, be prepared to tear into it (new sickle sections, rock guards, clamps, belt, etc).
Get the operator, service and parts manuals.
Sicklebars don't take a lot of horsepower but the larger ones (7-9 ft cutting bar) can be a heavy load for a smaller CUT. Check out the weight of the sicklebar before buying to be sure your tractor can handle it.
Some older sicklebars are hard to set up for proper cutting and need constant attention keep running properly. Also, sicklebars tend to clog while mowing heavy weeds/crops, meaning that you have to back up periodically so the clog gets cleared from the mowing bar.
Good luck