79 Cutlass Supreme brougham

I just bought a 79' olds cutlass supreme brougham, it is in damn near mint condition and it runs like a champ. Its only got 79,000 original miles on the 5 litir 307 v8 engine. I have a few questions, how many horse power is that engine? Was it a good buy? What are some things i could do to make it faster? and HOw about how much could i sell it for? Thanks!