Yes both sides. Yeah no need to retrofit, just dont' put HIDs in them, they are not set up for HID but the HIR bulbs work awesome.
OEM if you buy new is that price for the side markers IIRC but you can find good ones in any yard or on ebay or wherever for way less in good shape.
Also get the lisle headlight adjuster tool, its worth the $20 or so for the 94-98 lights and adjusting them.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.