I understand what you're saying about wheel speed, but wheel speed can be obtained from final ratio gearing IF you have enough torque to turn it, and to obtain that amount of available torque all you need is enough cubic inches and/or power adders. The whole reason for turning an engine at a high RPM is to pass a certain amount of fuel through it in order to produce a certain BTU/work ratio. Small cubic inch motors, theroetically, can produce the same #'s as a larger cubic inch engine but you have to pass the same amount of air/fuel through it as the bigger motor thus the need for more RPM's. Large cube engines can do this at a part saving lower RPM. Pounds of fuel per hour....lbs./hr is what determins the "work" produced.
Once again, 7K long term RPM is NOT recomended on ANY long stroke engine. You may get a properly built long stroke engine to turn a high RPM for SHORT periods of time (eg. 30 seconds of drag racing) but it takes it's toll. Hope this helps.
Rob