SF Giants Star Jake Peavy -- Turning Cable Car ... Into Mobile Bar!!!!

San Francisco Giants pitcher Jake Peavy is in the process of buying an authentic S.F. cable car to commemorate the big win ... and he's planning to turn it INTO A BAR ... TMZ Sports has learned.

How cool is that!?

We spoke with Jake's brother Luke Peavy, who tells us the whole thing is still a "work in progress" -- but they've already got the plans drawn out.

Here's the deal ... the Peavy family owns a 5,000-acre estate in Alabama called Southern Falls Plantation -- and the goal is to ship the cable car over to the property.

"Once it's in 'Bama, it will be turned into a mobile bar in Southern Falls," Luke tells us.

So, to make this clear ... if you're on the property, THE BAR WILL COME TO YOU!!!!

No word on when the Peavy's plan to have the bar in operation -- but the family is super-charging the process to get it done ASAP.