Well unfortunatly, back in grandads day, he didn't need a micrometer and plastigauge, because the engine he was working on was most likley initially built and assembled properly by the manufacturer. Maintaining something like this is a basic hand tools job in most cases. This is not always the case with a listeroid. This isn't a Cat or a Cummins or an original lister, it is a basic machine built by the lowest bidder in India! I used a dial indicator, vernier caliper and a machineists precision level to confirm the basic alignments when I built up my "Roid" kit. Nothing fancy, it is not what you got, but how you use it and harbor freight cheapies in most cases along with some straight edges and feeler gauges will tell the tale. My engine block of course was not aligned properly in several areas, the biggest being that the crankshaft was not perpendicular to the cylinder bore. Heck all 4 feet on the case weren't cast and ground level. I got lucky that the shortest 2 feet were on opposite corners. I made a file bar and used those 2 short feet to draw file the two tall feet down to the same level so the block would set without wobbling. The large holes in the sides of the case were machined incorrectly in India, and I did some minor machine work to the bearing carriers to correct this. The biggest tool I have in my shop is a drillpress. I had a friend with a lathe big enough to turn a bearing carrier in so I did that. I could have just about as easilly removed the required metal with a handheld die grinder, or even a set of hand files though. Because of machine inaccuracies like this, many roids will come with half gaskets under the cylinder base to force the cylinder to tilt one way or the other to align it with the crank. I don't know if the original CS's used half gaskets, but if machined properly, I wouldn't think them necessary... Most of the idler gear issues you will read about are as a result of sloppy machine tolerances in the case which lead to excessive gear backlash. Sloppier tollerances = less rejected parts. I wonder how many original lister CS's have gear train problems?
You want to know if you can handle a Roid? Go garage sailing and buy an old lawnmower, generator or rototiller with a briggs and stratton engine(heck, sometimes you can get them for free). Preferably one with a horizontal shaft. If you can pull one of these apart and put it back together, then a roid will be no problem, only bigger. The basic tools needed to do either engine are very similar.
Good luck
Ron