One minor correction to the Silverliner IV lists (as of today)
Silverliner IV (single units)
276-305 (some renumbered to fill gaps left when cars were renumbered into the 400-series)
400-416
Silverliner IV (married pairs)
101-188 (gaps due to renumberings into the 400-series)
308-399 (gaps due to renumberings into the 400-series)
417-460
Time to confuse you all more. The original 30 Silverliner IV's renumbered into the 400's were as follows:
401-410 (single units)
411-430 (married pairs)
I used to have a complete Silverliner IV renumbering conversion chart, including the 400-series cars that were renumbered twice (the original 411-416 were married pairs renumbered into higher 400's as single units were renumbered into the current 411-416).
Regarding the Bombardier fleet:
As a comparison, the original cars (2401-2410 and 2501-2525) were based on the NJT Comet IIb series delivered to NJT in 1987 shortly after the SEPTA order.
The center-door cars (2550-2559) were actually built to Metro-North Shoreliner III specs (except with the interior decor and seats matching our existing fleet). These cars were built and delivered at the same time as that last Metro-North order.
Since we're talking numbers, I'll fill you in on a plan SEPTA had to renumber the Silverliner II fleet (this plan was since scrapped). It would have seen the 9000-series ex-Reading Silverliner II's go into the 200-series as follows:
201-209
210 (former 9001, fills gap from original car wrecked)
211-219
220-239 (Silverliner III)
240-250 (former 9002-9012)
251-264
265 (former 9013, fills gap from original car wrecked)
266-269
270-273 (former 9014-9017)
"CSX Detector. Milepost Six Point Four. No Defects. Repeat: No Defects. Total Axles Seven Four Seven. Detector Out"