dˈuː tə ðˈɪs, ðɪ ˈɑːɹ θɹˈiːhˈʌndɹɪd nˈaɪnti dʒˌiːtˈiː wˈʌn bˈɛɹz ɐ ɹᵻzˈɛmbləns tə ðə dʒˈæɡwɑːɹ ˌɛksdʒˌeɪˈɑːɹ fˈɪftiːn, wˌɪtʃ wʌz ˈɔːlsoʊ dɪvˈɛləpt baɪ tˌiːdˌʌbəljˌuːˈɑːɹ ænd bˈeɪst ɔnðɪ ˌɛksdʒˌeɪˈɑːɹ nˈaɪn, ænd ɪn fˈækt jˈuːzd ɐ kˈɑːkpɪt ɪŋklˈuːdɪŋ ðə tˈʌb, ɡɹˈiːnhaʊs ænd ɹˈuːf lˈaɪn fɹʌmðə vˈɛɹi sˈeɪm tˈuːlɪŋ æz ðɪ ˌɛksdʒˌeɪˈɑːɹ fˈɪftiːn, wɪð sˌʌm kˈʌstəm tˈuːlɪŋ blˈɑːks ˈædᵻd tə ðɪ ˌɛksdʒˌeɪˈɑːɹ fˈɪftiːn tʃˈæsi mˈoʊld, ɔːlðˈoʊ fɚðɪ ˈɑːɹ θɹˈiːhˈʌndɹɪd nˈaɪnti, ðə ɹˈɪɹ ænd fɹˈʌnt ˈɛndz, ænd səspˈɛnʃən wɜː kəmplˈiːtli dˈɪfɹənt ænd wɜː dɪzˈaɪnd tə mˈiːt dʒˌiːtˈiː wˈʌn spˌɛsɪfɪkˈeɪʃənz, ðɪ ˈɑːɹ θɹˈiːhˈʌndɹɪd nˈaɪnti z tʃˈæsi wʌz lˈoʊɚ ænd wˈaɪdɚ, bˌʌt slˈaɪtli ʃˈɔːɹɾɚɹ ɪn lˈɛŋθ ðɐn ðə dʒˈæɡwɑːɹ, mˌeɪkɪŋ ðɪ ˈɑːɹ θɹˈiːhˈʌndɹɪd nˈaɪnti lˈɑːɹdʒɚɹ ˌoʊvɚɹˈɔːl.
Due to this, the R390 GT1 bears a resemblance to the Jaguar XJR-15, which was also developed by TWR and based on the XJR-9, and in fact used a cockpit - including the tub, greenhouse and roof line - from the very same tooling as the XJR-15, with some custom tooling blocks added to the XJR15 chassis mold, although for the R390, the rear and front ends, and suspension were completely different and were designed to meet GT1 specifications, the R390's chassis was lower and wider, but slightly shorter in length than the Jaguar, making the R390 larger overall.