Some time has passed from my lst post. Here are the advances:

I've mounted the spacer wood (a pice of a food chopping dish from WalMart) between the firewall and the engine mount. Drilled the screw holes, and put them in their place. Also glued six pieces of pine wood to fix the cowl.
I've planned to use aluminun tubes to route the fuel and pressure lines through the firewall, and that's what i've done. Also applied one coat of PPG's ClearCoat to make the wood fuel proof.