3 on the tree to a 4 speed, what do I need?

What year are we talking here? Which 4 speed? Did this to my '66 Valiant. If your current bellhousing is drilled for both patterns you can use it with a 4 speed that has a 4.35" bearing retainer. Mine wasn't but MaMopar started doing that around '68. If you have an 833OD you will need a bellhousing for the 5.125" bearing retainer. The clutch will work since it has 23 splines and you probably won't find an 18 spline transmission. Your crossmember and transmission mount will bolt to the 4 speed as well. Speedo drive and cable is a direct swap. You will need to change the front yoke on the driveshaft to the larger 727/833 yoke to match the output shaft on the tranny. Driveshaft length will be OK with just the yoke change. You will also need a shifter, shifter mount, linkage, and the floor hump for your particular car unless you like driving around with a huge hole in the floor. Pretty simple swap and most of the parts needed are already in place.