The cross-section of the bars was determined by the stuff I could find in my scrap box, so anything similar will probably do, providing it is strong enough. The bolt holes through the bar are sleeved with a bit of tubing, to prevent the bar from collapsing when the bolts are tightened.
The pulley is A Dayco 00032 (thanks to War Machine for that!)
The main bar is 40 x 20 mm, and started life as a shop display stand - wall thickness about 2mm. The alternator brace is 20 x 10mm solid aluminium alloy, and was part of an old photocopier.
The bolts are 118mm long, (not
including head), 22mm of which is threaded. Bolt diameter is
9.5 mm (3/8"). I got them from my "magic bolt box",
they probably came from a Chevy engine in the first place, possibly
starter mounting bolts by the look of them. Don't know what the
thread is, approx 16 TPI
These measurements were taken to help a friend. Absolutely no warranty is given as to suitability or accuracy.
However this has been on my car now for over 6000 miles with no problems.