Yup, no worse than a 4" in a small block with a 6.123" rod. The B block with a 4.250 and a 6.535" rod is actually a little better int he rod ratio department. No its not as good as 3.75 with a 6.760 rod, but as long as you keep the rpm in check it will last for a long time.
And here is a testament to the short rod + small bore + long stroke = loads of bottom end torque.
Nice solid build Brain. A tire melter for sure.