Vulcar Ingot has some extras in Grand Theft Auto IV: custom front bumper, skirts and a hood. It's the VD90R version.
Due to some game limitations I wasn't able to make the hood work in game. Nevertheless, I've converted the front bumper and skirts.

To add the tuning parts you need to have fastman limit adjuster installed.

Installing the tuning parts:
1. Add the DFF files in your game (in gta3.img or ModLoader folder doesn't matter). 
2. Use Free ID List Generator (http://www.gtagarage.com/mods/show.php?id=16944) to get full list of free ids.
Copy ingot_mods.ide in veh_mods folder (it's inside GTA San Andreas\data\maps).
Copy vehmods.fxt into CLEO_TEXT folder (it's inside GTA San Andreas\cleo).
Open the ingot_mods.ide file and make sure the IDs are free. If they're not then change them to free IDs.

Also, if you have replaced Solair (or any other vehicle) make sure to change the TXDfile identifier for tuning parts from Ingot to Solair
Example. Before:
11813, misc_a_ingot, ingot, 100, 2097152
After:
11813, misc_a_ingot, solair, 100, 2097152

Save and close the file.
Open gta.dat (it's inside "...\GTA San Andreas\data\" folder) and find these 2 lines:

# vehicle upgrade models
IDE DATA\MAPS\veh_mods\veh_mods.IDE

Add this line right after the veh_mods one:

IDE DATA\MAPS\veh_mods\ingot_mods.IDE

Save changes and exit the file.
3. Adjusting limits in fastman limit adjuster. Open fastman92limitAdjuster_GTASA.ini and find these lines:

; IDE : objs section type 1 (14000) 
#IDE Objects Type 1 = 14000

; IDE : objs section type 2 (70)
#IDE Objects Type 2 = 70
Make sure to REMOVE the # symbol in the beginning of these lines and then increase the limits by:
Type 1: 1
Type 2: 1

Type 1  - undamageable parts (1 custom skirt in this example - misc_a_ingot) 
Type 2 - damageable parts (1 custom front bumper in this example - fbmp_a_ingot)
These lines should look like this:

; IDE : objs section type 1 (14000) 
IDE Objects Type 1 = 14001

; IDE : objs section type 2 (70)
IDE Objects Type 2 = 71
4. Open shopping.dat file (it's in data folder). Add the following lines in CarMods section (between "section CarMods" line and the 1st "end" line):
		fbmp_a_ingot		INGOTBU		respect 0 	sexy 0		1000 	
		misc_a_ingot		INGOTSK		respect 0 	sexy 0		800 	


Scroll down and find these lines:
	section carmod1 # Normal Cars
	type CarMods
Add these lines in the carmod1 section (after "type CarMods" line and before the next "end" line):
		item fbmp_a_ingot
		item misc_a_ingot
Save changes and exit.
5. Open carmods.dat and replace the line you added before\add one if you haven't done it yet\replace the existing line if you replaced vehicle (solair one for example):
ingot, fbmp_a_ingot, misc_a_ingot, bnt_b_sc_m, bnt_b_sc_l, exh_b_l, exh_b_ts, nto_b_l, nto_b_s, nto_b_tw, rf_b_sc_r, spl_b_mar_m, spl_b_bar_m, spl_b_bbr_m

Save changes and exit. 
Now you can check it out in your game. 