Using R5 parts on R4

[snes]

I've been looking on the GSF site - they dont offer R4 parts, but do for R5. eg. brake calipers - girling. I have these on my 4. The same part?
Head gasket sets - the R5 set, 1.1 engine, 85 onwards. Same as my 86 1.1 R4 engine?
Can anyone advise?
Thanks - bit of a noob at all this!

 

[mr-reno-139]

virtually nothing from 85 on R5 is same
pre 85 there are alot of interchangeable bits on R5s
seem to remember Euro Car Parts website still lists r4 parts
Quinton hazell certainly did when i last looked although dont think you can buy direct from their website but will give you some part numbers and an idea of parts available from uk suppliers
a lot of motor factors rely on a computer database these days but most dont list r4 as a searchable option even though the parts are quite often available if you can give them a part number first