I will throw out one more obscure option available to you. The deck height on the 2.4L XK 6 cylinder engine block is only 225mm, 67mm shorter than the 3.4/3.8/4.2 variants (292mm). That could be the 2-1/2" clearance you are looking for, without expensive racing parts.Viewed from the top, it looks like any other Jag six. Uses the same cylinder head. The engine from the 240 saloon even used a straight port head. Most Jaguar people can’t ID one on sight. It’ll be your secret. For your purposes, it could be a winning compromise.
