Squeak in front end of '66 289 coupe at speed

If its disc brakes in the front then that's what I would suspect first . Does it disappear if you maintain that speed and push on the brakes? get worse? better? no change?
Second I would suspect maybe a wheel bearing out of grease (Front end lube job does not include greasing wheel bearings) That only takes care of non rotating parts/joints and yours is a rotating part noise.

Just tell whoever you take it to the same thing you posted here. You don't have to tell them what you think it is or what was done to fix it before. A reputable shop can easily figure it out. Read reviews of the shop and try to find a local shop that works on classic cars not a local quiky lube or something like that.

One thing you can do also is go to a week end cruise in and ask around. You'll either find a guy there that can figure it out and maybe even fix it for you or you'll get names to reputable mechanics.

two things to check here;

1) as tos noted the wheel bearings. all too often they get dry from a lack of service. it might be a good idea to have them repacked anyway.

2) the spring perch. the bushing tends to deteriorate on them, and you get metal to metal contact and they will squeak badly, though usually going over bumps.

3) (ok three things, i lied shoot me) the front brakes. sometimes when the brakes are done, the mechanic leaves out the anti rattle springs, and you get a squeaking sound from them.

We'll expect some ice cream in the mail.