Another Datsun Tranny Question

Greetings
The filler plug on the 210 tranny I will install soon is very stuck and was
already looking somewhat rounded off when I got it.  
Can I safely apply propane torch heat to it to help in the removal process?

Does anybody know if the plug is a standard thread (pipe or variation) or
size?  I called one of the local Nissan dealers and he said he would have
to order it from Japan.

Thanks
Dave