If it was my car I'd go with a modest compression 505. Probably keep it down in the 9.50 range for compression with a small hyd roller cam and then put a Holley Sniper on it. We just finished an engine like that up the other day and it was smooth as silk. Had about 20 inches of vacuum and made close to 600 torque. It made around 500 on hp but it was all over by 5000 rpm due to the small cam. Keep the cam small and it will drive nice and smooth with decent mileage. The Holley Sniper with a Hyperspark ignition system gives you complete computer control over the AFR and the timing curve so you can dial in the tune at cruise. Costs some money to build an engine like that but it would be a fun car. Might even surprise a few BMWs with it.