The first prototype of the B25 was the NA40 - which had rounded wingtips:
The next was the NA-40B, or NA-42 (different sources disagree on it). No pictures I could find. It was lost in a crash. A further refinement was the NA-62, which was the final basis for the production model.
If the only distinctive difference between a "classic" B25 and your bird were the wingtips and engines, I would suspect that it was a B25 with "aftermarket" engines rated similiarly and with a slightly modified wing. Wouldn't be the first warbird who someone did a little "tinkering" on.
Personally, I always preferred the B-26 Marauder....