For a manual gearbox IRS pan with torsion bar front, your only option is the 1976 Beetle - and not many of them left.
The '68-70 1500 Beetle semi-auto is another option, but you'll have to convert to manual if you don't want semi-auto. The manual Beetles of those years were swing-axle.
Your only other option is to replace the Superbug pan's frame-head with a torsion bar frame head and beam. A good VW workshop could do this for you.
If you use a 76 pan and the vehicle is registered using the original 76 chassis number.......then your car must comply with the ADR's for 1976.................this includes emissions, and anti burst doors, and a 58 shell does'nt have anti burst door looks !!