Well originally the ships were going to be Romulan so that might be why that happened.

Well, they should have been Romulan. Since when has there been a Neutral Zone between the Federation and the Klingons? The very fact that we've had so many disputes over planets (Capella IX, Sherman's planet, etc.) argues that there can't be a Neutral Zone with the Klingons.

And in Star Trek III, the Klingon ship has a cloaking device. This has always been explained away by saying there was a short-lived alliance, the Romulans gave them the cloaking device in exchange for their ship designs. But when you think about it, does it make sense they'd give away their ONLY tactical advantage to a race they hate?

Well remeber the Klingons and Romulans hated each other in the 24th century not the 23rd century.

Unless Worf is really really old.

According to Worf, they have hated each other for centuries.

That apparently didn't stop the Klingons from selling the Romulans D7 battlecruisers.

Maybe they stole them. Or captured them in war. I don't know...

Or the Klingons were more selective about who they held grudges against back then and sold the Romulans some ships to get cloaking tech.

Especially since the Romulans had little ships at the time and the Klingons could of seriously f@#ked them upif the Romulans tried to steal stuff from them.