Gentlemen,
Thank you for replies.
Yes, I know about all problems associated with J-box configuration. I will be happy to install S&C Vista line-up, but money is an issue (and physical size of equipment).
Original system (with 3 J-boxes 1in-3out)worked for last 35 years (indoor installation, no dust, scheduled shutdowns for cleaning, DLRO connections, visual inspections).
Do you mean bus duct?
Kind of... with bolt-in cable logs.