I make mine from an oak board. Use a drill press to drill the thru hole. I used a piece of oak from my kitchen floor project. The plank is about 1/2 inch thick, so I cut it in to 1/2 inch width using table saw. Now I have a board 1/2 inch square. cut to length. Then drill the thru hole. The hole thru the oak is parallel to the grain of the wood. Works well and you can make various lengths easily. I have 2 or three degrees of right thrust, and the firewall is square. So I make two of the standoffs shorter than the other two. Put the short ones on the right. I even cut the ends at a slight bevel (2 or 3 degrees) so that they meet the firewall squarely and the back of the engine evenly. The longest I have ever needed was about one inch long.