Is it possible? I have version 1.0, just checked, i musta patched it when i first installed it(i didn't think it was version 1...) Well anyways, i downloaded a supra model, and it was gunna have me replace the feltzer, and i like it so i just added the lines that it said to replace feltzer with to the end of the lists of cars in all the appropriate files, renamed the felzter diff files that are for the supra to "supra.diff" and that txd one or w/e, and in my model viewer the supra shows up, but the second i click new game and the loading screen comes up SA crashes. is there something i missed? these are the edits i did. 
carcols.dat 
Supra, 1,1, 3,3, 4,4, 6,6, 7,7, 8,8, 20,20, 43,43   put this liek right after the super gt 
carmods.dat 
Supra, nto_b_l, nto_b_s, nto_b_tw, bnt_b_sc_p_l, bnt_b_sc_l, bnt_b_sc_m       again, right after super gt 
handling.cfg 
Supra        1250.0    4000.0   2.0    0.0 0.3 -0.1  75  0.65 0.80 0.50         5 235.0 23.0 10.5 F P   8.0   0.55 0 30.0       1.4  0.76  0.0   0.27 -0.10 0.58 0.3            0.2  0.53 39000         0               400000          0  1    0      placed this one right before glendale 
vehicles.ide 
612,	Supra,          Supra,          car, 		Supra,          Supra,          null,   executive, 	10, 	0,	0,		-1, 0.748, 0.748,	 0   added htis before end and right after entry id 611 
then i added the files Supra.diff and Supra.txd to the gta3.img file,  
then last I made a new entry in the language file /text/american. w/e, new entry name Supra with value Supra 
Thanks in advanced for any info/help/suggestions.