Good to see there is a relaxed approach on this. Taking your time is important. Smart idea on another block.
Before anybody starts in with the engine build advice, we all are going to need to know a few things. Is there a 1/4 mile goal? Or just the above description of power on demand? Is this mostly for curie? Hwy. driving? Is there an RPM at which you would like to cruie at? Once we all know and have an idea on where the build is going we can suggest a gear ratio/tire combination which will work in your favor. "Gregsdart" has a pretty sweet combo that may fit into your plans. Crackedback mentioned an excellent builder. If your so inclined and local enough, I'd use his guy.
As you mentioned in your opening post, the 904 will do just fine. No need for the 727.
On gears, you can select those first or last. If you select them last, there ratio is adjusted for the engine set up. If you pick them first, the engine is adjusted for the gear ratio to be used.
Confused? Look at it this way.
If you know you want to cruise the Hwy. once in a while for a few hours or hundred miles, & cruise at around no more than 3300 RPM's, a 3.23 and stock size tire will do that. This limits the cam size. Adjusting the tire size to a larger diameter will lower the rpm. (Possible smaller cam) Adjusting the gear ratio upwards to 3.55 to bring up the RPM (Back to the cruise RPM or higher) will allow a larger cam.
Don't get caught up in a big cam thinking. It is not always needed.
