The part that has failed has these markings:

LS1176
8AT
D5HT

This is the data sheet for it, I think:

SN65ALS1176:
www.cgi/http://www.allcomponents.ru/pdf/ti/sn65als1176.pdf

although how to I tell if the failed one is a 65 or 76 prefix part?

Searching local suppliers, I find this:

SN75LBC176A:
http://www.jameco.com/Jameco/Products/ProdDS/251053TI.pdf

Is the second a suitable replacement for the first?

Package is SOIC.

They're both TI, so why the different numbering (1176 vs 176)? What does
65/75 prefix indicate? And regarding the other markings on the failed IC:
does HT mean Hi-Temp?

A few too many discrepancies in my mind to just swap it in just yet.

Thanks,
--
John English