I've never heard of this 'neutral kit' either. I don't know what that means.
The only Ranger that can be safely flat towed is a 4x4 with a manual shift case. You could install a manual shift transfer case on a 2wd to make flat towing easier. The lube part of the t-case is mounted on the rear output part so the t-case will be lubed when the rear driveshaft is spinning. The electric shift is the same, except there is no neutral and the tranny tailshaft will be spinning--not good when the pump isn't running--as was stated in a previous post.
Make damn sure that if you have auto hubs they are actually unlocked before flat towing. If you pulled the driveshaft from an electric shift case and the front hubs were secretly engaged, that would piss you off a couple thousand bucks later.
The limit on flat towing is 35mph/50miles max is you don't have a manual case. I know of a Ranger that went 100,000miles with occasional use behind an RV with the driveshaft on. I don't know how many actual miles it was towed but it did kill the tranny eventually.