73 Valiant Driveshaft length with 8 1/4

[C2ndLTpigeon]

My 73 Valiant is a 318/904 it currently has a 7 1/4 that will be changed out to an 8 1/4.

How much would I have to shorten my current shaft? What would the overall length be?

Thanks

 

[H22A4]

7.25" to 8.25" driveshaft?

 

[C2ndLTpigeon]

Do you happen to know if you can buy a new driveshaft anywhere?