The earliest version of the MXR+ used an LM741CN integrated circuit, as Pedal Area states there is only a small difference between this IC and the UA741CP (which I already had in my parts stash) but since these are fairly cheap and I'm going for vintage accuracy as much as possible I decided to buy some LM741CN. It also uses 1N270 germanium diodes (which I had never ever heard of before) so I had to track some of those down, which was easy enough on ebay.