Re the space frames, you get what you pay for. Is it tigged, migged, or stick welded? How square? How flat? Are the pieces CNC cut? What kind of design went into it, newer theories or another copy of something in the 60's? They can be overengineered also. Too much for what people want to pay. I have JBL. Fits into the latter categories. But I wouldn't have it any different

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And the time it takes to put one together correctly is another consideration. Buying parts, waiting for arrival, shipping charges, some taxes, mistakes....... The right tools.......
It's amazing really what the major manufacturers put together in the way of high performance vehicles nowadays. Engineering vs. cost.