Here's a few pictures of the GT-1544 next to the GT-1548. The GT-1544 has the wastegate on it now, normally the GT-1548 has it's also, but just not in this picture. The turbine wheels are almost the same size, but the GT-1548's exhaust inlet and housing are much bigger, and the compressor wheel and housing are also quite a bit larger. The '48 flows a lot more air, and has provisions for water cooling.