Paul.....if it is not to much trouble for you....... i would suggest you to read project section with few topics where restorations are made from scratch, and you will find answers to most questions you have.
I did the same thing when was preparing for doing mine.
Among many good topics two were revelation to me to realize in witch direction i would go with my restoration.
First
http://www.renault4.co.uk/forum/threads/1985-renault-r4-f6-restoration-project.3173/
Second
http://www.renault4.co.uk/forum/threads/r4-restoration-made-in-france.3140/
And of course Malcom's restoration section of his web page...
So many details and do-it-your-self descriptions where secrets-of-the-job are shown....
Be patient as this forum is not "hot" and answers are not coming in a minute but they certainly do come...
As to your questions here are my experiences.
135R13 and 145R13 tires were standard to R4. Aldo 135R13 was more on saloon models and 145R13 on van models (due to load)
Today you put what ever tire you can find easily.
I am driving on 155/70/13 (same diameter and hight as 135/80/13)
Here is topic with more detail explanation
http://www.renault4.co.uk/forum/threads/tyre-sizes.7354/
For antifreeze i have used 2 lit concentrate (-30°C) + 3 lit distilled water to get mixture for my climate.
Distilled water is better solution as it is "clean" and wont left sediments in cooling canals. And it is cheap ( at least here in Croatia 5 liters less than 1 GBP)
For oil filter i use standard size as it is quite close to body and did not ever tried to experiment with bigger one.
Believe that more efficient is to change oil every 5000 to 8000 km with new oil filter