Oh my sweet giddy aunt. That really looks fantastic. Well done sir, well done! I was marvelling at your interior work, and had forgotten that when I designed the kit that it included all this detail.
@Mol_PMB Yes, the kit is designed to be able to take a 35mm wheelbase Black Beetle. I bought one for test fitting just to make sure.
Some googling shows that you could use a Tenshodo equivalent motor bogie.
http://motorbogies.com/index.php?main_page=product_info&products_id=304