My own experience re used bits is very positive . I bought a 54 s/a A10 which when started sounded like the proverbial bag of spanners , both mains completely shot and the crank ( small journal ) knackered . Being like most of us (who were around in the sixties ) at 17 I was always skint but had friends one of these found a plunger motor from a guy who we knew , He was adamant that the motor was a good 'en and I took his word and paid the princely amount of £5 plus some bits I had for a bubble car ( one of Willies finest ) I just had an idea that the plunger crank would drop right in same as barrels and pistons fingers crossed etc. I stripped and cleaned and even polished the doner bits and the s/a cases, fitted new big end shells, moved the d/side main from plunger cases to s/a and in my nivety simply transferred the main . The result was a motor that started 1 time after I'd oiled by kicking it with plugs out until it returned to the tank , idled wonderfully and then wouldn't break no matter what I did to it!! and remember stupid a 17 yr old can be. I've often thought about that rebuild and would like to think that the extra care preparing everything before reassembly outwayed the s/hand element of the bits. I also remember another slant on the R/R info about 2 posts back, when selling Ford cars a couple of years later a brand new Cortina wouldn't start, had to have the head lifted to sort it and every piston was a different size from standard to 40thou over all as sloppy as hell ,no compression worth speaking about ,selective assembly Ford called it ,you can imagine what we called it Regards BobH.