[ultraflo]

For a non-power adder, nearly stock combo with unported E7 heads... I'd go with the 1 1/2" equal length shorties.

If you are going to further you modifications down the road, then the 1 5/8" may be a viable alternative with that route in mind.

Keep in mind that the NMRA R/S guys are limited to 1 3/4" unequal length short-tube headers and 2 1/2" exhaust and they run in the low 10's (nitrous cars and blower cars alike, w/ class mandated stock camshaft).

I mananged 10.0's with 1 5/8 - 1 3/4 -3" Bassani longtubes on an EFI 306 w/ a 200hp NX single nozzle kit.... going off that, I'd say the 1 1/2" headers are plenty for a nearly stock 5.0 ....IMHO