I like this a lot and Olds power or no power is my moto. I also have a 2004R with a 260 and 3.42 gears, both help. Get at least dual exhaust on the car. Sounds better and helps, don't be scared to through on 2.5" pipe. I had 1 5/8" Sanderson Shorties with 2.5" dual exhaust with a compact X pipe. If I had even a slight stall it would have left rubber and pulled strong through the rpms, it didn't feel like a 260. I took it off but I am putting it back on, currently less than 2" dual exhaust on the car, decent off the line but really struggles past 3000 RPM, the 4200 RPM shift point sounds really labouring for the poor baby Olds. So put the 2004R in with 3.42 or 3.73 gears and add your dual exhaust and headers if you find a 350, don't rule one out, especially with the new 4" stroker crank or a 403. Then you can take your time building the motor and still have something that will get out of it's own way and get good mileage doing it. Good luck with your search, c'mon local guys help him out.
cuttywhtnite, let me check around my father in laws. I had a good 403 covered in his barn. May still be there if he hadn't got rid of it. As soon as I can get out there, maybe Saturday morning, I will let you know.