Hmmmm..... converting HH tech to/from Traveller.
You'll need LBB5 and/or FFS. Make the Manties TL14 or 15, with the Peeps 2 tech levels below the Manties.
For the weapons, I'd make Traveller turret weapons the "countermissile launchers (CM)/point defense laser clusters(PD)" of HH. The missile launchers of HH would be bay missile launchers. Make bay plasma guns the broadside laser mounts, and bay fusion guns the broadside grasers. Smaller ships (up to CLs) use 50-dton bays while the big ships use 100-dton bays. If you later want to have battleships and superdreadnoughts fighting you might want to invent bigger, more powerful bay weapons (or look here:
http://home.comcast.net/~steveosmanski/New_HG_weapons_mounts.htm). Play around with the ranges so that missiles really (by a factor of 10) outrange beam weapons, but beam weapons get a small range bonus if firing at the bow or stern of the target (no sidewalls there, at least at first). Turret weapons can't damage ships that have armor or sidewalls, but can be used against unarmored/unshielded targets.
For defenses, armor is armor although you might want to create a simple system to allocate armor to the six sides of the ship (top, bottom, bow, stern, port, starboard). The drive wedge makes the top and bottom invulnerable as long as the drive is up.
The sidewalls are something you'll have to invent. Their strength is always proportional to the ship size (until the uber-tech of later books) and they degrade gracefully (one hit won't take out all your sidewall on one side) and don't seem to take up much space. They must be fairly expensive since civilian ships don't usually bother.
As for the drives, the Traveller jump drive can become the hyper generator of HH, although there's no need for jump fuel in HH. Each level of jump becomes about 1.5 levels of hyperspace the ship can reach. Most warships carry a hyper generator that lets them reach the Theta hyper bands.
Traveller maneuver drives can be the impeller drive of HH, just remember to adjust the "G" ratings accordingly and also remember that the drive is always split up between two drive rooms (forward and aft) and is subdivided into "nodes," some of which are bigger and more necessary (alpha nodes) than the more numerous beta nodes. The "inertial compensator" that keeps getting shot in the HH books could be bought as part of the maneuver drive but is located separately and can be hit on its own.
As for converting ship sizes, I'd use the "one bay weapon or 10 turrets per 1000 dtons" rule of LBB5 and build ships that way, getting the weapons numbers from the HH books and/or Ad Astra's "Saganami Island Tactical Simulator" game, if you have it.
Rough weapons fits/ship sizes:
early LAC - 4 missiles, 4 beams, 6 PD = 9000 dtons
Chanson-class DD - 10 missiles, 6 lasers, 12CM, 12 PD = 19,000 dtons
Apollo-class CL - 14 missiles, 14 lasers, 14CM, 14PD = 31,000 dtons
Star Knight-class CA - 20 missiles, 12 beams, 26CM, 26PD = 38,000 dtons
Reliant-class BC - 52 missiles, 34 beams, 32 CM, 32PD = 93,000 dtons
Peep ships tend to have more missiles, fewer CMs and more PDs.
For small craft, there's really only two: the "cutter" and the "pinnace/assault shuttle." HH cutters are about the size of Traveller cutters (50 dtons) but can only accelerate slowly (no impeller drive). Pinnaces are at least the size of Traveller shuttles (95 dtons) and have impeller drive so they are quite fast (not as fast as ships) and they have room for a full platoon of troops in battledress.