I can get you a price, one set of heads are 088, the other set is 12562934, which are gm factory replacements, identical to the 088s. Both sets are in great shape with isky valve springs matched to the cams.
Are those the style you need?, and the problem is shipping them will be pricey because the are heavy.

The L29 heads are not peanut ports, they are large ovals. I have built several small budget L29 engines with these heads and should be right around 450hp but its never been on a dyno. I run a crane 731 cam in my L29 on a stock cast rotating assembly, air gap dual plane intake, gil exhaust and a pro form 750. sounds and runs great

The L29 heads have a strange combustion chamber. It has a large chunk of steel in the combustion chamber I think to help a swirl condition for the intake charge. That chunk of steel is prone to cause detonation. I've used these heads in multiple combinations, the total timing must be limited to 27 - 28 rather than the usual 34 - 36. They are not a good choice for performance builds, if they are all you have check your air fuel ratios under full load and keep them rich.

Why not call Bob @ Marine Kinetics?

http://www.marinekineticsonline.com/

HP 500 carb'd cam will get 450hp, Mercruiser used it on their 454 HP450. They used square port heads but I bet torque would be better with the ovals.
You need a cam with close to .600 lift to get there