Is300 parts for sc300
 

Is there any is300 parts that can fit 96 sc300 manual trans?

Aftermarket parts? I believe a Treadstone aftermarket exhaust manifold will bolt up although that may only be for 2JZ-GE VVT-i cylinder heads rather than pre-1998 Non-VVT-i cylinder heads.

OEM parts? There are some odds and ends I'm sure but the 2001-2005 IS300 has a different version of the 2JZ-GE engine (VVT-i) compared to the 1997 and earlier SC300's 2JZ-GE. The IS300 M/T's W55 transmission and dual mass flywheel will technically fit an SC300 chassis and 2JZ but it's a weaker transmission than the W58 that the 1996 SC300 M/T came with from the factory.

The IS300 has a different rear differential the design of which is not shared with the SC/GS/MKIV but which is shared with the following vehicles: JDM Altezza, MX83 Toyota Cressida (and many of the similar Japan-only 1JZ performance sedans from the 1990's such as the Mark II, Chaser, etc.), the 1986-1992 Supra MKIII (all), Scion FR-S, Subaru BRZ and Toyota GT86.

The driveshafts are different, subframes are different, etc. The bodies have very little in common except for their both being designed during an era of high Toyota over-engineering and probably each car uses some random and uninteresting Toyota parts bin pieces.

The only main exception to all of this which is very commonly used on 92-00 SC's are the sporty three-spoke IS steering wheels and their matching Lexus "L" center airbags (which can be wired up using a special Toyota adapter harness-- if you can locate one of those). The same steering leather wrapped (although with sometimes varying style leather and perforations) wheel design was also used in the 1998-2005 Toyota MR2, the 1998 Toyota Supra (all trims), the Toyota Matrix XRS and Corolla XRS.

I believe if you check the flange on the end of IS300 header it will have two tubes to a flange to connect to the mid pipe that matches the two tubes from the header. I also believe the diameter of two tube flange goes into a pipe that is 2 1/4" or 2 1/2" where the SC300 is 3". I believe this would be the same as the stockIS300 set up. Please correct me if I am wrong.

OEM parts? No. Unless you have a 98+ VVTI SC300. Then you can use the majority of 2JZ-GE VVTI engine parts.
This even goes for the manual trans in the IS300. It's a W55 (your 96 SC is a tripod W58) so it doesn't even sit in the stock location correctly and that trans is known to hold less power than a W58.

If you are talking about aftermarket performance parts, almost all mechanical 2JZ-GE VVTI and non VVTI parts are interchangeable. You just may run into clearance issues with certain parts.
You CAN bolt a performance IS300 header to a SC300 but you will need the 98+ SC300 Y-pipe, or modify an aftermarket IS/GS300 Y-pipe to fit.