Welcome to TBN! You will find just about everything you will need to know to keep your Yannie running right here on this board. A 40"-42" brush hog would be about the right size for a 1401D. Even with a cutter this small you will want some front weight as a counterbalance. And a 48"-52" tiller would be about right also. Yanmar 2-pt tillers ride very close to the back of the tractor, so front counterweights aren't as much of an issue with the tiller.
The attachment should come with the shaft. The shafts can be quite expensive to buy so they are often removed from used equipment. A close coupled tiller must come with the drive shaft for I have found it just about impossible to find the correct replacement shaft. Your tractor will have the industry standard 1-3/8 6 spline shaft. This is a exceptionally common shaft.
If you haven't done so already...it's a good time to convert your two point to a three point hitch. It will standardize your tractor and allow you to use any three point implement sized for your 1401D.
Allis Chalmers 416S John Deere LX280, John Deere Z225 zero turn yanmar 1401 , Oliver 550 Special, Oliver 75 Lawn Tractor, New Holland 3930 4WD, Mitsubishi BDF2 Dozer
I converted my 1401 to 3 pt. however I kept the attachment for my 2 pt. Yanmar tiller. I think the 2 pt. tillers operate better than those with the 3 pt. conversion.