i have a 400c on LPG with an appropriate cam and valves. considering i will put an a larger carby (if i don't go straight gas) what is the best manifold dual or single plane? this motor is only a whisker off standard, but does have higher comp due to aussie 302 heads on it. should i go for the spacers (some quite pricey) and access all the standard cleveland gear, or try the edelbrock,weiand etc available? Cheers.