One of tghe first things I did with my 305 besides having it bored, was to install a edelbrock performer dual plane intake with a 600 cfm carb. Was good for an estimate 12HP. Headers,cam. etc. brought it near 290HP. I was going to put a dual quad w 2 500 cfm carbs but was told to much carb for that engine. With a small blower and a 700 cfm carb should make a big difference. Just be sure to mate a cam with the blower and keep you compression down to no more than 8 to 1 or you won't be able to have full boost levels. Maybe others have tried a blower on a 305 and could give you more info.