Some Altair questions, if I may..

Working away on the Altair 8800 restoration.. So the display/control board ("d/c") is now installed, and I'm running into my first roadblock. I ask your understanding in advance, as my familiarity with digital logic is pretty weak. This machine has a Processor Tech. MB-1 mainboard in it. Full-width, 16 slots, and some mods I don't understand. First, there's an LM309 (TO-3 case) mounted to the board, apparently providing reg'd 5VCD to the normally 8V (un-reg'd) line. Why would that be there? Every plug-in board I've seen - which isn't all that many, admittedly - has its own regulator for 5V on-board. Secondly, on the far left side of the board, there are several columns of resistors that seem to be doing a couple different things - some are pulling-up various groups of lines to what seems like 1/2 of VCC, others are either there for termination or some other unknown function. All together, close to 100 resistors installed there.. and it's clearly a mod (at least partly) as a line of 50 new holes was drilled to accommodate them. Anyone know what's up with this stuff? Why it's there? At this point, my sense is that I need to remove all of it, as they don't exist in the original build - and I may even cut the main board in two - totally lop-off the leftmost 12 sockets along with the resitors & reg.