Just a quick note on this... the VDO gauge is made to go with the electric VDO sender, regardless of what car it's on... it's a standard resistance range, anyway. (0-180 ohm) The thread pitch is BSP, just like the original.. there is no adaptor... the sending unit has a low-level contact to wire to the idiot light.... It's as simple and clean as can be.
I have the DIN panel and I don't know what the issue would be with the vacuum hose on the boost gauge being mounted anywhere else.
As to the wheels... I agree it's a pricey upgrade but losing 24lbs. of wheel and adding almost an inch of track width really made a big improvement in the handling. (I admit I wouldn't have done it if I hadn't hit a driveshaft on the highway and ruined one wheel.) So now it's a Christmas present.
-C