import new component into LT Spice with .cir file
The AT-310 subcircuit works because it uses a .model that is accepted by LTspice (.model NPN ...). The model for ATF34143 uses an unrecognized type, GASFET. Changing GASFET to NMOS, or VDMOS, which are recognized by LTspice, results in a running simulation, but with warnings saying that certain parameters are ignored (since they are not known what they mean). Thus, the result of the simulation should not be considered.

To see what types are supported, see the LTspice help at LTspice &gt; Circuit Elements &gt; M. MOSFET. Unfortunately, none of the levels (1:6, 8, 9, 12, 14, 73) seem to fit this particular model. So it looks like bad luck with this part for LTspice. Maybe other simulators.