I have a 400 that is leaking anti freeze out of the back bolt on the right side. Are there any quick fixes for this?

 

is the bolt lose over time they will loosen up
if you have too remove the bolt [after draining the coolant system] and clean it add a sealant to the threads re-install and tork to specifications "quick fix" if it is the bolt it could be the back of the manifold gasket is leaking at the water jacket
or you could remove the manifold and re-install new gasket set check the remaining water jacket ed bolts for rust and wear