So if I understand, the 16" from the bracket to the firewall on Mechie's 818 is where the axles fit? Where the brackets are, that's where the axles fit? I am trying to see exactly where the middle of the axles fit wrt the firewall on the 818.
Then yeah, not possible to modify the brackets as anyway the VR6 axles will still be at an angle with the wheels.
Moving the gas tank probably means re-doing the rectangle frame around it too, as the frame is also at 15-16" from the axles and may well hit on the top and/or bottom of the VR6 front end.
I mean, looking at that, if the axles to the front of engine are not exactly 16" (or less depending on the engine's shape), I don't see how any engine could fit.