Re my PV444 the most bonehead thing I've done so far was not checking the rear axle I bought from a so called specialist last year. Because I mounted a B20F, I wanted to replace the original 4,56:1 rear axle by one with a 4,1:1 final drive.
I asked for the latter and supposedly got a 4,1 axle, which I cleaned, painted and mounted. I didn't hesitate to send my speedo away for recalibration after counting the number of revs of the speedo cable on a certain distance. But then I was told that wasn't necessary as it appeared to give almost 100% accurate readings... That was suspicious. I reinstalled the speedo and a small tachometer as well and went for a test drive... to find out that the engine made 4000 rpm at a speed of appr. 65 miles. Yes indeed, I had replaced my original axle with one that had exactly the same final drive... A lot of work, a lot of cost, all for nothing (almost).