What plug size for 727 speedo hole?

I am not going to use a speedometer
cable with my big block 727. Does anyone
know what size freeze plug will fit? Thanks.

i just modified a coin,i think it was a nickle,and some rtv ,used the speedo cable threaded collor and snugged it down.

1 49/64

Dorman 555-037 1" 49/64 4 speedo delete

Thanks guys 👍