Simon is right - you can't be too careful. There are some good items about, but there is also a lot of junk. I bought a ‘professionally’ built 302 short engine that was ‘race prepared’ with all the right bits. However, when I had it checked over some months later by a reputable engine builder, the real problems emerged. His comments were it looked like the guy had gone through the scrap parts bin and put any items together that would fit so he could sell them on – it would never have run!
Ok – the motor had an internally balanced steel crank (but it was down to +40 thou and one big end has picked up, so it’s unusable and can’t be ground down any more). The block had been worked on, but one of the main journals has spread, so it’s also junk. It had been built up with some 289 rods, which are just too long and stick out of the block by about 50 thou. Even the cam was U/S. Out of all the bits, only the set of +30 TRW pistons are usable. Given what I paid for it, these must be the most expensive ones you can get!
My advice - spend a little more and go to someone who is recommended - at least then you have some comeback!!!