4 Speed advice needed please!!

Hi all! Quick question, i Have a Australian Valiant basically the same as a Plymouth valiant with a 383, 727 and 8 3/4. I only use the car for race days and the occasional cruise. Even though its a 383 car its light in the front similar to a sb so handles pretty well with all the mods i've done. Obviously a manual trans would suit my purpose better and i'm at a crossroads whether i should change. I have a chance to do a straight swap with a guy , my BB727 for his BB A833. comes with clutch bellhousing etc. It will prob be a pain to change the bellhousing to put the clutch fork on the right hand side as we have right hand drive cars. But mostly i don't know what these boxes can handle?? The car will be putting out real close to 500hp with a cam upgrade and i run a locked diff. Will the strain of a manual be too much for the diff as well?? Thanx for your replies as i would need to act fairly quick on this opportunity.