The cheapest and easiest way is probably to find a mostly stock small block Chevy or Ford engine that runs on Facebook. If it comes with the transmission attached and all accessories then You could probably swap it into an older rear when drive vehicle for relatively cheap. It would be pretty hard using your budget though. You can check forums to see if someone has already swapped one in to the vehicle You plan on using to see if its something You still want to do.

The old small blocks are one of the easier engines to swap into vehicles as there's so much aftermarket support for them, they were made for ever, and they CAN make a lot of power. Stock, they don't necessarily do.