Car Has No Power But Still Shifts Into Forward, Reverse and Neutral

I have an 83 d150 with the 360. Not sure on the tranny. Since buying this truck, there has been some clanking and grinding in the tranny, inconsistent shifting when starting off and no downshifting when accelerating at highway speeds. Last night, I go out and start it up, and let her get warmer up like I do every time I go for a drive. I don’t make it to the end of the driveway before I loose all fluid and power. Will still shift and engage in forward, reverse, neutral, and park, but has zero power. Any ideas on what’s going on?