When using the cam mark and crank TDC method to check the chain, it is of the
utmost importance to turn the engine over by hand from the crank damper bolt in the normal
RUNNING direction. It can be turned the other direction, but that will give a false reading as you are then pulling from the chain tensioner slack side.
Although off-set keys can correct these,
it is much easier to change a streched chain with a new one with a repair link.
The link is connected to the old chain and
pulled around the gears by the old one . The link is then refitted to the new chain. Fairly simple.
As you mentioned that there has been a couple of head jobs done , there is also a possibility that someone may have shaved the head, which could could change the distance between the cam and crank, resulting in your reading. Others may know more on that.
As a good test for a worn chain, be it any chain,is to turn it sideways held out-streched and see how much it droops on the far end.
Compare to the new one before installing and it will give you an indication as to the difference in condition.
As these 113 are mechanical FI, your pump is
also timed by this chain and a worn chain directly affects the the fuel metering, so
that is another reason, aside from valve timing, to change the chain out when they show any wear.