So, was shortening a pair of front struts the other day, and thought I would post my home solution to cutting a strut tube for shortening.
I think that all vintage Datsuns (and a lot of other brands) use a 2 inch outer diameter tube for their front struts. When I wanted to cut some struts to shorten them (to lower the car), I lacked a tool or machine to get the cuts square before re-welding, so I came up with an inexpensive solution. I bought a 2 piece shaft collar (about $20 from McMaster Carr), and used it as a guide to grind the tubing.
You can use your band saw or saws all (reciprocating saw) to cut the tube, and leave a bit extra hanging out. Clamp the collar around the tube, and then use an angle grinder with flap wheel, or a sanding disk to grind the tube back to the collar (flush). Repeat on second part of the tube, and you have two nearly perfect surfaces that you can weld easily. Chamfer the tube before welding to insure penetration.