Cheapest way to built a 300-350hp small block

I think the cheapest way is with a magnum.
LA 360 are 25 years old, chance of finding a good one in the junkyard is slim.
I bought a 94 360 mag off a member here for $200, when I tore it apart it still had the cross-hatches in the bores, the motor had well over 100K miles on it.

Food for thought.

http://www.magnumswap.com/