Sorry I'm late…..

Congrats on getting her running!
Yes, agree with you & cletis. I'd use NEW 10 gauge wire if you're inserting a 50 AMP Maxi in that line. You can get a holder and fuse that will mount in a convenient location so you can visually inspect it in the future. Then in the future you can also power stuff safely from that point using it as a distribution point.
As long as you're at it …. go here for more wisdom on electrical matters….. This guy is great!

http://www.madelectrical.com/index.shtml

He's saved a lot of our butts over the years! He guided me on a delicate modification to a 76 Rolls Royce that had a burned up alternator and regulator. $1500 for a new Alternator
and $250 for a new regulator!! (They were beautiful castings, but $1750
for delivering 12 volts was out of my league!)
He helped me understand how to keep the Rolls Royce idiot light, but converted to an internally regulated Chevy alternator from NAPA for $69; plus it had a lifetime warranty at the time! Problem solved.
mike