Well the chassis for the 787b is way too long for the RX-7 LM. I have thrown these codes together real quick using your ideas and filling in the blanks. I will leave the code tags on so you can see what cars the parts are from. Making it easier to find them v4 codes. Any code that does not have a tag is fron the RX-7LM. Here is a full set of codes to build that car. Unfortunatly for you they are in GS2v2/AR2 encryption, but are good parts if you want to convert them, or look them up at sinned's page. At least if someone else wanted to build this car they could use these codes as well.
RX-7 LM Race Car
GS2 US slot 1
CarBase 1C041350 - 482097C3 1C041354 - EF9F906E rx7_lm_race_00
BodyColor 1C041358 - 1456EAD5 1C04135C - 1456E7A6 Blue
body & downforce 1C0413C8 - A84C827A 1C0413CC - ABB33A9C
CarType 1C041360 - 1456E7A6 1C041364 - 1456E7A5 Race
brakes 1C041368 - 077CA8F5 1C04136C - A96690D4 Normal, _787b_91
brake controller 1C041370 - 1456F706 1C041374 - 1456E7A5
chassis 1C041378 - 2A4AB3B8 1C04137C - 6DB7473A gt40_race_69
engine 1C041380 - 0FCC28F5 1C041384 - A96690D4 Normal, _787b_91
drivetrain & VCD 1C041388 - E84C761F 1C04138C - 2F3312A6 VCD, fto_lm_race_00
transmission 1C041390 - A84C7C9F 1C041394 - 77B33A9C
suspension 1C041398 - A84C811A 1C04139C - 6FB33A9C
LSD 1C0413A0 - E84C7579 1C0413A4 - 30B312A6 Full, fto_lm_race_00
front tyres 1C0413A8 - 52CDFCC2 1C0413AC - 68EBCAA3 T5 II Medium, lotus_99t
rear tyres 1C0413B0 - 32CDFCC2 1C0413B4 - 68EBCAD4 T5 II Medium, lotus_99t
weight reduction 1C0413C0 - 67339210 1C0413C4 - DB600E41 Stage 3, _180sx_x_96
polish 1C0413D0 - DF3E032A 1C0413D4 - 299FC726 Polished, rx7_rz_00
balance 1C0413D8 - 381E032A 1C0413DC - 299FC7AA Balanced, rx7_rz_00
displacement 1C0413E0 - 872C7D69 1C0413E4 - EB049CBE Increased, civic_r_98
computer 1C0413E8 - 1456E7A5 1C0413EC - 1456E7A5
NA tune 1C0413F0 - 1456E7A5 1C0413F4 - 1456E7A5
turbo 1C0413F8 - A84C82F6 1C0413FC - 2CB33A9C Stage 3
flywheel 1C041300 - 2FCE032C 1C041304 - 299FC78A Full-Racing, rx7_rz_00
clutch 1C041308 - 08FE0345 1C04130C - 299FC75E Triple Plate, rx7_rz_00
shaft 1C041310 - DF8E032A 1C041314 - 299FC71A Carbon, rx7_rz_00
muffler 1C041318 - F76E032C 1C04131C - 299FC736 Full-Racing, rx7_rz_00
intercooler 1C041320 - D88E032B 1C041324 - 299FC7D2 Racing, rx7_rz_00
I would suggest some high DF, this car will be rediculously high powered most likely.
Front DF 1C041274 - 1456E703 2.30
Rear DF 1C041278 - 1456E70F 2.50
And finally the supershine
dirtyness 1C041550 - 61DFB00C
If you are building the car from scratch, put in those first four codes and check the garage to make sure they worked. The safest way to avoid mistakes is to put the other part codes in one at a time. Easier to find a mistake in one line of code instead of searching through a thousand characters.
