I have some friends/neighbors that did a C150 conversion:
Taildragger Aviation - N180EF Conversion and Restoration The earliest C150's still had C140 gearboxes in them, as well as the new mounts for the nosewheel mains. I don't think the 150's had a nose heavy problem though. I would think the difference in CG between a nosewheel and tailwheel 150/2 would not be huge. The parts are not super heavy and the lever arms are small.
The main advantage the converted 150 has over the 140 is real flaps!