42RH in 68 Dart advice/request

As far as special tools needed for the OD the only thing a person MIGHT need would be the depth gauge tool. However there are ways around that as well. As far as compressing the spring you can use a 3” PVC coupling and cut a slot in it to access the snap rings while it’s in a press (trust me I know I have first hand experience as I just rebuilt one about a month ago). You can also use the intermediate shaft as an alignment tool of the splines and use a piece of 3” PVC to compress the OD clutch hub and instal the snap ring.