Thanks guys,

I've looked more at the MAPP now as you guys suggested, and a few others from various Google results, mentioning Propane not being as effective for heating.. I also looked into Oxy+Gas options, but the price is much too high for me, at least at this stage.
How effective do you think the MAPP would be on that boss? Or bolts/nuts etc.. of that size/thickness ?

Xhall: I've tried WD40, Penetrating oil (homemade with Acetone and ATF) aswell as soaking in Vinegar overnight (Vinegar seems decent enough for bolts and such). Still can't make it budge.

Only other option would be to cut it off and replace it. Those attachments though seem to cost around $30.. seem a bit much for a single part. I do have a spare boss here I recently salvaged.. not sure if it's the right fit though.

Thanks again, muchly appreciated smile