TIM . . . BLOW THAT BABY!!!! Forget about a 12 port head if you are going to be stuffing it with a compressor. Siamesed ports give you more staging volume and more even flow than you would get with dedicated runners and some argue the properly prepared siamese head flows better in certain conditions anyway due to the smoother flow of air rather associated with 2 cylinders pulling rather than the start / stop associated with only one pull every two revs of the motor. (not my words . . . but those of guys who get into the 10's in the 1/4 mile with siamesed heads)
[censored] Larrowe makes a cast intake for a 236/261 that allows bolt on of a Weiand blower or a B&M or a 4/6-71 blower - $400 for the casting ready to bolt onto your head, but you have to do the final machining (drilling mounting bolts) for your particular blower and make your own gasket or pay them $ to do it for you. Front bearings on these motors dont really like the side load to drive the belt but nothing is free when adding power to a 6.
Another book you need to look at is "Supercharged" by Corky Bell. Get it at Amazon.
After you read this book (and Leo Santuccis book Fred mentioned - not for your motor, but for the principles) you will be much better prepared to select the right cam, carb setup, timing setup, etc.
Have fun!!
