I' m not aware of any easy after market triggers WITH a safety for the Arisakas. I know that Timnet is recently producing a trigger for it but it does not have a safety.
With the safety issue and the cost of dealing with swapping out the barrel, I think you' d be better aff starting with a different receiver for your project. I' ve seen a few nice Arisaka sporters, but they were fairly gadgeted-up crossbreeds.
Have you already fired it as is? You might try just reaming the chamber to 30/06 dimensions and using the expander ball for a Arisaka 7.7 in your die. You can still buy bullets from 100 grains to 215 grains in the .311 caliber. If your barrel is toast then this is obviously not an option.