How much is a 440 motor, and would it be a good swap....?

Recommend you go with the 360 small block for that swap as it will drop in their easier and it is cheaper to buy and easier and cheaper to buy performance parts for. Check out www.summitracing.com for pricing and parts. Also you will need to completely change your mounts, the slant six will have one really high mount and one really low mount and you will need to cut them off and put the proper level mounts for the V8 on their so you will need a welder for this or you can swap out the entire sub frame for a V8 one if you would rather avoid the welding. Good luck!