Based on the power they get from the Mazda 4 cylinder engines I find the power of 375bhp not that surprising.
I read in an article saying Frontline are quoting 10 inch wider track. The pictures do look lightly wider but it is hard to know how they did it, the car doesn't look that much obviously obviously wider. Simon do you know what bits they widened?
From my knowledge the wheelbase is 91 inches or 231.1cm, front track 4 foot 1 inch or 124.4cm and rear track 4 foot 1.25 inches or 125cm. Adding 10 inches should leave the wheel base alone and make the front track 4 foot 11 inches or 1498mm and rear 4 foot 11.25 inches or 1505mm. Based on their website I feel wheel base of 1520mm is a typo, Front Track 1490mm is about 9 3/4 inches wider and Rear Track 1540mm is about 11.4inches wider. The rear of the car does look slightly wider than the front so it probably has been increased by a larger margin.
Out of curiosity how do you change the track on a MGB? Can you change it a few mm with adjustments or need new parts regardless, I assume 10 inches needs a lot of custom parts.