First pic is the SCART to TV connector setup. I did not use shielded cable anywhere inside the TV. I didn't before and didn't have an noticeable issues, so I didn't this time and it gave me a chance to try out using ribbon cable.
I actually used the three ground pins on the SCART connector intended for wire shielding for grounding the RGB 75 ohm termination resistors and then tied those three pins to the main grounding pin. I opted to use these "J-Tag" ribbon cable connectors, these are 10 pin, but you only need 8 pins for this setup. I suppose you have two additional spots for wires if you needed something more.
This is the back of the little prototyping board. It contains all three RGB inline resistors (910 ohm on the diagram) and the diode on the blanking line.
Bottom of the main TV board.
This pic shouldn't necessarily be used as reference for soldering locations! This is a bit more messy than it needs to be, due to things going poorly during the previous mod work. So ignore the two small heatshrinked wires jumping across. Only issue I had this time were removing the jumper wires to insert the OSD RGB diodes. They hook the wires around which made it very difficult to get all the solder out. I only had one of the pads lift on me, but in retrospect this probably could've been avoided by using my hot air station or approaching the problem with the iron in a different way, which is how I believe I got the others out without lifting pads.
But yea, ribbon cable keeps it pretty straight forward and clean. There is very little room between the bottom of the board and the bottom plastic of the TV case which is another reason the ribbon cable worked well. Haven't noticed any interference issues yet.
Finally, the board sitting in the TV. Because the board slides into a tray thing at the bottom, squeezing the ribbon cable through that hole is sort of a must, unless you were to route it in a complete opposite direction towards the power supply side of the board.
This is the pic I took of the TV back when I originally did the mod with the OSD switch. With the muxing setup, that RGB/OSD switch is no longer there.