Arsenal Saiga SGL-31 or Bulgarian SLR-105 are the best. Don't let anyone fool you otherwise.
Saiga 5.45 is next and a basic conversion to pistol grip is easy and cheap IF you don't care about looks. Great bang for buck. For a full conversion to a `74 clone, unless you can do a lot of the work yourself, the SGL-31 is a better deal. Just add up the cost of parts - furniture, fire control group, gas block, front sight base, brake, hand guard retainer, proper rear sight, feed ramp, proper trigger gaurd (or welded up the stock one), etc. plus add the labor to press off and on parts, weld up extra holes, rivet feed ramp and refinish and you gonna end up spending more that the 31's base price of $799.
SAR-2, WUM-2, Romak-2 (NOT WASR-2) are next; though ruff they clean up good. Kit builds from reputable makers are here too, remember the kit is used with god-knows-how many rounds through them. Note: I'm assuming orginal barrel there. Some US barrels in current builds have had issues working with certain ammo.
ETA: apparently the Lancaster builds are the ones to avoid, atleast here lately. Strangely, I haven't heard of a lot of issues with Century's `74s and I think they are out there for ~$350 from certain vendors.