where to find old ICs ?

I am trying to collect a few spares of some old ICs so that I can continue to maintain my older DEC PDP equipment. Last night I diagnosed a bad 74H00 in my PDP 11/45 and when I realized that it was a hard to find component and that it was only going to get more difficult to find, I created a list of parts which I might need and do not have. If anyone has additional information about any of these parts (data sheets for the ROMs, etc.) or information on possible substitutes, it would be appreciated. Also, if you know of a source for these parts, that would be good too. --tnx --tom DM8598-AB ROM DM8598-AC ROM DM8598-AD ROM 3101 256x4 ROM 3101A 256x4 ROM 74187 256x4 ROM 74182-1 look ahead carry generator (fast version ?) 74194 4-bit bidirectional universal shift register 74H01 quad 2-in nand gates w/open collector outputs 74H10 triple 3 input nand gates 74H21 dual 4-in and gates 74H22 dual 4-in nand gates w/open collector outputs 74H30 8-in nand gate 74H40 dual 4-in nand buffers 74H50 dual 2-wide 2-in and-or-invert gates (one gate expandable) 74H74 dual d-type positive edge triggered flip flops w/preset & clear 74S15 triple 3-in and gates w/open collector outputs 74S65 4-2-3-2-in and-or-invert gate w/open collector output 74S74-45 fast version (4.5ns) of 74S74 ? Where these parts made by or for DEC? DEC380 DEC380A DEC8001 DEC8251-1 DEC8815 DEC8815A DEC8875 DEC8881 DEC8885 DEC9318 Also some transistors: DEC4258 transistor DEC30098 transistor