Strange ..I would nearly chance a guess that it may have been used as a sander instead of a bandsaw..
Tires look to be in good nick thickness wise , any lumps taken out of them ?
Why would someone not have all these parts :x
I've heard Inca's are good wee machines before .
First things first
I would work on the tensioning mechanism first ,
On the Elektra Beckum bs315 I recently worked on I noticed the tensioning screw was simple threaded bar...
It looks like its made to be replaced oftenish ....
Figure this out first, as it looks to be a stout saw that might handle having no guides for a brief period of fun/motivation .
I would be looking to get a tuffsaws blade for it and tracking it correctly ...even by hand if you do not wish to use it.
This might keep you going for a bit...
I don't know if you wish to get the parts for the saw, or get a welder (if you dont have one allready)
I keep seeing small welders going for 40 to 50 euros where I live ...Lidl even do them, and people are always upgrading
them ...maybe to a mig or just bigger? there out there .
Get a small angle grinder and buy thin 1mm melt yer clothes discs, in the pound shop .
You go through them fast and their expensive probably 1 pound a disc (better value in the multipacks
If that fails, shop around ,maybe in large auto shops for cheap ones.
A good few files too in the pound shops ,shop around for the best ones , should b only 2 quid a file .
Table trunnion should be next to fabricate, and after that it depends on what you are going to do with the saw...
The frame looks fairly sturdy, so you might get away with a bracket bolted temporarily for use ....
It depends on what your doing with it ...how long till you plan on needing guides ....
If you need precision (guides help a bit)you need the guide post/toolpost.
that rack and pinion looks tricky to fabricate if you were to....there is easier ways to do this, if you cant get the part...
I'd look for possible clones of that saw if your dead set on getting the rack and pinion to adjust for post travel.
Then comes the guides ...if your making the guidepost from scratch ...you might want to figure out
how to go about mounting the guides into your design.
But I found it can be confusing thinking up something from scratch ...and even if the original design looks more complicated ..
its designed allready and a sure thing, so you can just plow on and it will take up less time than hmmm and hawwing over it.
Remember its not Matt Cremona's machine your building ...from the beginning, there is end in sight
Plenty of suggestions here on this forum .
Good luck with getting your machine going