Does one of these exist? I know of one based on VR2, but I'm not sure if there was an SR3/Matrix based one as well.

I wonder if a R3R vehicle calculator was ever finished? I know at some point an Excel-based one was going around in development stages.

I'd been working on one some years ago, but it was just too hairy for me at the time. I'm eventually planning on doing a big rework of the vehicle design/customization rules for SR3R, at which point such a calculator would be really useful, so I might yet make one. Don't hold your breath, though—big stack of issues on the table for before I get there.

~J